Innovative antibody enzyme manufacturing technology

Abstract

A method for producing an antibody κ-type light chain having enzyme activity or improved enzyme activity includes: a modification step for modifying a polynucleotide encoding an antibody κ-type light chain in which the variable region is a polypeptide comprising an amino acid sequence in which the 95th amino acid residue from the N-terminal of the variable region by the Kabat classification is a proline residue so that the proline residue is deleted or substituted to obtain a polynucleotide encoding an antibody κ-type light chain in which the variable region is a polypeptide comprising an amino acid sequence in which the 95th amino acid residue from the N-terminal of the variable region by the Kabat classification is deleted or an amino acid residue other than a proline residue; and an expression step for expressing the antibody κ-type light chain having enzyme activity by an intracellular or extracellular expression system using an expression vector including the polynucleotide encoding an antibody κ-type light chain from after the modification step.

Description

[Technical Field]

[0001] The present invention relates to an innovative antibody enzyme production technology. Specifically, it relates to a production method for imparting enzymatic activity to an antibody κ light chain or improving the enzymatic activity of an antibody κ light chain. This application claims priority to Japanese Patent Application No. 2019-136403, filed on July 24, 2019, the contents of which are incorporated herein by reference. [Background technology]

[0002] Antibodies are composed of heavy chains (H chains) and light chains (L chains). The heavy and light chains are composed of variable regions (VR: Variable Regions) and constant regions (CR: Constant Regions), and the variable regions have hypervariable regions (CDR: Complimentarity Determining Regions). Furthermore, antibody light chains are classified into κ and λ types.

[0003] In recent years, antibodies with enzyme-like activity, i.e., antibody enzymes, have been attracting attention. Because antibody enzymes combine the high molecular recognition ability of antibodies with enzymatic activity, they are expected to be applied in many fields, including medicine, the chemical industry, and the food industry. In particular, antibody enzymes that are highly specific to target molecules and can damage target molecules through their enzymatic activity are expected to become excellent anticancer drugs with few side effects. In particular, human-type antibody enzymes are expected to have few side effects when administered to the human body, so pharmaceutical companies both in Japan and abroad are eagerly awaiting the development of useful human-type antibody enzymes.

[0004] The inventors have so far conducted various original studies on antibody enzymes (see, for example, Patent Documents 1 to 4, etc.).

[0005] For clinical use of antibody enzymes as pharmaceuticals, it is important to be able to stably mass-produce antibody enzymes with sufficient activity. However, many antibody enzymes have insufficient enzymatic activity, and when artificially synthesized using intracellular or extracellular expression systems using genetic recombination technology, their performance is unstable and there are large differences between batches. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2006-197930 [Patent Document 2] International Publication No. 2011 / 102517 [Patent Document 3] International Publication No. 2013 / 133253 [Patent Document 4] International Publication No. 2015 / 025786 Summary of the Invention [Problem to be solved by the invention]

[0007] A primary object of the present invention is to provide a method for producing an antibody enzyme comprising an antibody light chain with higher enzymatic activity, and a method for stably producing such an antibody enzyme with excellent storage stability. [Means for solving the problem]

[0008] The inventors discovered that an antibody κ light chain with higher enzymatic activity can be obtained by deleting or substituting the proline residue at position 95 from the N-terminus of the variable region, as determined by the Kabat classification, in the amino acid sequence of the antibody κ light chain. Furthermore, the inventors discovered that a composition containing an antibody light chain with higher activity can be stably obtained by incubating the antibody light chain with one or more metal ions selected from the group consisting of Group 10 elements, Group 11 elements, and Group 12 elements in the purification step of its production, and then removing the metal ions, thereby completing the present invention.

[0009] That is, the antibody κ light chain according to the present invention and a method for producing the same are as follows: [1] to

[12] . [1] A method for producing an antibody κ light chain having enzymatic activity or improved enzymatic activity, comprising: a modification step of modifying a polynucleotide encoding an antibody κ light chain, a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue; an expression step of expressing the antibody κ light chain having enzymatic activity in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain after the modification step; A manufacturing method comprising: [2] The method according to [1], wherein the antibody κ light chain is human or mouse. [3] The method of producing according to [1] or [2], wherein the variable region of the antibody κ light chain having enzymatic activity or improved enzymatic activity is a polypeptide selected from the group consisting of the following (1a) to (3c): (1a) a polypeptide consisting of an amino acid sequence represented by SEQ ID NO: 1 in which the proline residue at the 95th position from the N-terminus according to the Kabat classification is deleted or substituted; (1b) A polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (1a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (1c) A polypeptide having an amino acid sequence that has 90% or more identity with the amino acid sequence of the polypeptide of (1a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (2a) an amino acid sequence in which the proline residue at the 95th position from the N-terminus according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 2 has been deleted or substituted; (2b) A polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (2a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (2c) A polypeptide having an amino acid sequence that has 90% or more identity with the amino acid sequence of the polypeptide of (2a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (3a) an amino acid sequence in which the proline residue at the 95th position from the N-terminus according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 3 has been deleted or substituted; (3b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (3a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (3c) A polypeptide having an amino acid sequence that has 90% or more identity with the amino acid sequence of the polypeptide of (3a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue. [4] The method for production according to any one of [1] to [3], wherein the variable region of the antibody κ light chain having enzymatic activity or improved enzymatic activity is a polypeptide selected from the group consisting of the following (4a) to (7c): (4a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 4; (4b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 4, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (4c) a polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 4 and consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (5a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 5; (5b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 5, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (5c) a polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 5 and having a deletion or an amino acid residue other than a proline residue at the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification; (6a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 6; (6b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 6, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (6c) A polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 6 and consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (7a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 7; (7b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 7, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (7c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 7, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue. [5] The method of producing according to [1] or [2], wherein the variable region of the antibody κ light chain having enzymatic activity or improved enzymatic activity is a polypeptide selected from the group consisting of the following (8a) to (8c): (8a) an amino acid sequence in which the proline residue at the 95th position from the N-terminus according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 8 is deleted or substituted; (8b) A polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (8a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (8c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence of the polypeptide of (8a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue. [6] The method of any one of [1], [2], and [5], wherein the variable region of the antibody κ light chain having enzymatic activity is a polypeptide selected from the group consisting of the following (9a) to (9c): (9a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 9; (9b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 9, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (9c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 9, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue. [7] an expression step of expressing the antibody κ light chain in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain; a first purification step of obtaining a crude product containing the antibody κ light chain from the expression product obtained in the expression step by column chromatography using a column containing a first packing material; an addition step of adding a metal ion to the crude product containing the antibody κ light chain to obtain a crude product containing an antibody κ light chain complex in which the antibody κ light chain and the metal ion are bound; a second purification step of obtaining a purified product of the antibody-κ light chain complex from the crude product containing the antibody-κ light chain complex after the adding step by column chromatography using a column containing a second packing material; a removal step of removing the metal ions from the purified antibody κ light chain complex product obtained after the second purification step to obtain a purified antibody κ light chain product; A method for producing an antibody κ light chain, comprising: [8] The method for producing an antibody κ light chain according to [7], wherein the removal step is carried out by adding a chelating agent. [9] The method for producing an antibody κ light chain according to [7] or [8], wherein the metal ion is one or more selected from the group consisting of copper ions, nickel ions, zinc ions, gold ions, silver ions, and platinum ions.

[10] The method for producing an antibody κ light chain according to any one of [7] to [9], wherein the variable region of the antibody κ light chain is a polypeptide consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue.

[11] The method for producing an antibody κ light chain according to

[10] , further comprising, before the expression step, a modification step of modifying a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus according to the Kabat classification is a proline residue, so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus according to the Kabat classification is deleted or has an amino acid residue other than a proline residue.

[12] A method for imparting enzymatic activity to an antibody κ light chain that does not have enzymatic activity, or for improving the enzymatic activity of an antibody κ light chain, comprising: the variable region of the antibody κ light chain having no enzymatic activity is a polypeptide consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region is a proline residue according to the Kabat classification; A method comprising modifying a polynucleotide encoding the antibody κ light chain that does not have enzymatic activity so that the proline residue is deleted or substituted.

[13] An antibody κ light chain, the variable region of which is a polypeptide selected from the group consisting of the following (4a) to (7c): (4a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 4; (4b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 4, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (4c) a polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 4 and consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (5a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 5; (5b) a polypeptide consisting of an amino acid sequence represented by SEQ ID NO: 5 in which one or several amino acids are substituted, added, or deleted, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (5c) a polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 5 and having a deletion or an amino acid residue other than a proline residue at the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification; (6a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 6; (6b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 6, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (6c) A polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 6 and consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (7a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 7; (7b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 7, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (7c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 7, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue.

[14] An antibody κ light chain, the variable region of which is a polypeptide selected from the group consisting of the following (9a) to (9c): (9a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 9; (9b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 9, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (9c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 9, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue. [Effects of the Invention]

[0010] The antibody κ light chain obtained by the production method of the present invention has higher enzymatic activity than conventional antibody κ light chains, and is expected to be a pharmaceutical with wide clinical applicability. Furthermore, the method for producing an antibody κ light chain according to the present invention enables stable production of a highly active antibody κ light chain. [Brief explanation of the drawings]

[0011] [Figure 1A] 1 is a cation exchange chromatogram for the control case (no copper ions added) in Example 1. [Figure 1B] FIG. 1B shows the results of SDS-PAGE (non-reducing) of each peak in the cation exchange chromatogram shown in FIG. 1A. [Figure 2A] 1 is a cation exchange chromatogram for Case 1 in Example 1 (copper ions added after primary purification and copper ions removed after secondary purification). [Figure 2B] FIG. 2B shows the results of SDS-PAGE (non-reducing) of the peaks in the cation exchange chromatogram shown in FIG. 2A. [Figure 2C] 1 shows a cation exchange chromatogram of the human antibody κ light chain purified in Case 1 of Example 1 (addition of copper ions after primary purification and removal of copper ions after secondary purification) after storage at 4°C for 3 months. [Figure 3A]1 shows cation exchange chromatograms of human antibody κ light chain immediately after purification in Case 2 (addition of copper ions after primary purification) in Comparative Example 1, and after storage at 4°C for 3 days and 3 months. [Figure 3B] FIG. 3B shows the results of SDS-PAGE (non-reducing) of each peak of the human antibody κ light chain in the cation exchange chromatogram shown in FIG. 3A after storage at 4° C. for 3 months. [Figure 4A] 1 is a graph showing the change over time in the degradation activity of human antibody κ light chain (S35), human antibody κ light chain (S34), and human antibody κ light chain (S38) towards FRET-Aβ peptide in Example 2. [Figure 4B] 1 shows the amino acid sequences of the variable regions of the human antibody κ light chain (S35), human antibody κ light chain (S34), and human antibody κ light chain (S38) in Example 2. [Figure 5A] 10 is a graph showing the change over time in the degradation activity of human antibody κ light chain (T99) and human antibody κ light chain (T99 P95Δ) towards FRET-Aβ peptide in Example 3. [Figure 5B] FIG. 1 shows predicted three-dimensional structures of the variable regions of the human antibody κ-type light chain (T99) and the human antibody κ-type light chain (T99 P95Δ) in Example 3. [Figure 6A] 1 is a graph showing the change over time in the degradation activity of human antibody κ light chain (H55) and human antibody κ light chain (H34) towards FRET-PD-1 peptide in Example 3. [Figure 6B] 1 shows the amino acid sequences of the variable regions of the human antibody κ-type light chain (H55) and the human antibody κ-type light chain (H34) in Example 3. [Figure 6C] 10 is a graph showing the time-dependent change in the degradation activity of the human antibody κ light chain (H34) towards FRET-Aβ peptide, FRET-Tau peptide, and FRET-PD-1 peptide in Example 3. [Figure 6D] 10 is a high-performance liquid chromatogram of a solution after a degradation test of a PD-1 peptide by a human antibody κ light chain (H34) in Example 3. [Figure 6E]FIG. 1 shows the results of SDS-PAGE (non-reducing) of each solution after the degradation test of recombinant human PD-1 and human serum albumin (HSA) in Example 3. [Figure 6F] 10 is a graph showing the change over time in the degradation activity of the human antibody κ light chain (H34) and the human antibody κ light chain (H34_P95(+)) towards the FRET-PD-1 peptide in Example 3. [Figure 7] 1 is a graph showing the change over time in the trypsin-like p-nitroaniline (R-pNA) degradation activity of mouse antibody κ light chain (InfA-15L) and mouse antibody κ light chain (InfA-15L P95Δ) in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] In the present invention and this specification, the term "antibody κ light chain" refers to an immunoglobulin κ light chain. The κ antibody light chain gene is constructed by selecting and rearranging genes from the Vκ gene cluster, Jκ gene cluster, and constant region gene cluster present in germline genes. The origin of the antibody κ light chain is not particularly limited, but is preferably mammalian, and more preferably human or mouse.

[0013] In the present invention and this specification, the term "anticancer agent" refers to a drug that has the activity of killing cancer cells or suppressing or inhibiting their proliferation.

[0014] It is well known in the art that some amino acids among the amino acid residues constituting a polypeptide can be easily modified without significantly affecting the structure or function of the polypeptide. Furthermore, it is also well known that, in addition to artificial modifications, there are mutants in natural proteins that do not significantly change the structure or function of the protein. In the present specification, the term "mutation" refers to the substitution, addition, or deletion of one or more amino acids in a specific amino acid sequence X.

[0015] <Method for producing antibody κ light chain> [First embodiment] The method for producing an antibody κ light chain according to the first embodiment of the present invention (hereinafter sometimes abbreviated as "the production method according to the first embodiment of the present invention") is a method for producing an antibody κ light chain having enzymatic activity or improved enzymatic activity, and comprises the following steps in this order: a modification step of modifying a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue; an expression step of expressing the antibody κ light chain having enzymatic activity in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain after the modification step.

[0016] According to the production method according to the first embodiment of the present invention, an antibody κ light chain having higher enzymatic activity than conventional antibody κ light chains can be obtained. Next, each component of the manufacturing method according to the first embodiment of the present invention will be described in detail below.

[0017] <Modification process> In the modification step, a polynucleotide encoding an antibody κ-type light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, is modified so that the proline residue is deleted or substituted, to obtain a polynucleotide encoding an antibody κ-type light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue. By carrying out this step, enzymatic activity can be imparted to an antibody κ light chain that does not have enzymatic activity, or the enzymatic activity of an antibody κ light chain that exhibits only low activity can be improved. In other words, this step can also be referred to as a "method for imparting enzymatic activity to an antibody κ light chain that does not have enzymatic activity" or a "method for improving the enzymatic activity of an antibody κ light chain." Here, improving the enzymatic activity of an antibody κ light chain means that the enzymatic activity of the antibody κ light chain after modification is improved by, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, 300% or more relative to the enzymatic activity of the antibody κ light chain before modification.

[0018] The method for modifying the polypeptide so as to delete or substitute the proline residue can be carried out by using well-known techniques to easily mutate the proline residue located at position 95 from the N-terminus of the variable region according to the Kabat classification in the amino acid sequence of the variable region, among the amino acid residues constituting the polypeptide. For example, any base in a polynucleotide encoding the polypeptide can be mutated according to known point mutagenesis methods. Alternatively, a deletion mutant or substitution mutant can be prepared by designing a primer corresponding to any site in a polynucleotide encoding the polypeptide.

[0019] <Expression process> In the expression step, the antibody κ light chain is expressed using an expression vector comprising a polynucleotide encoding the antibody κ light chain after the modification step, in an expression system known in the technical field, such as an intracellular or extracellular expression system.

[0020] When a recombinant expression system is used, a polynucleotide encoding the antibody κ-type light chain of the present invention can be incorporated into a recombinant expression vector, which is then introduced into a host capable of expression by a known method, and the polypeptide obtained by translation in the host (transformant) can be purified. The recombinant expression vector may or may not be a plasmid, as long as it is capable of introducing the target polynucleotide into the host.

[0021] When introducing a foreign polynucleotide into a host in this manner, it is preferable that the expression vector incorporates a promoter that functions in the host to express the foreign polynucleotide. Methods for purifying recombinantly produced polypeptides vary depending on the host used and the properties of the polypeptide, but the use of tags, etc. makes it relatively easy to purify the target polypeptide.

[0022] When a cell-free expression system (cell-free protein synthesis system) is used, it is preferable to add a polynucleotide encoding the antibody κ light chain of the present invention to a solution containing components necessary for protein translation and synthesis, such as ribosomes and t-RNA, and incubate the solution at an appropriate temperature to purify the synthesized polypeptide.

[0023] Examples of cell-free protein synthesis systems include systems using wheat germ extract, systems using rabbit reticulocyte extract, systems using Escherichia coli S30 extract, and systems using extracts of cellular components obtained from devacuolated plant protoplasts. Generally, eukaryotic systems, i.e., systems using wheat germ extract or rabbit reticulocyte extract, are selected for translation of eukaryotic genes. However, any of the above synthesis systems may be selected taking into consideration the origin of the gene to be translated (prokaryote / eukaryote) and the intended use of the protein after synthesis. Various commercially available kits can be used as these synthesis systems.

[0024] Since many virus-derived gene products express their activity after translation through complex biochemical reactions involving intracellular membranes such as the endoplasmic reticulum and Golgi apparatus, the addition of intracellular membrane components (e.g., microsomal membranes) is necessary to reproduce various biochemical reactions in a test tube. Extracts of cellular components obtained from devacuolated plant protoplasts are preferred because they can be used as cell-free protein synthesis solutions that retain intracellular membrane components and do not require the addition of microsomal membranes.

[0025] As used herein, the term "intracellular membrane component" refers to organelles composed of lipid membranes present in the cytoplasm (i.e., intracellular granules in general, such as the endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, and vacuoles). In particular, the endoplasmic reticulum and Golgi apparatus play important roles in post-translational modification of proteins, and are essential cellular components for the maturation of membrane proteins and secretory proteins.

[0026] The antibody κ light chain of the present invention can also be isolated from cells or tissues that naturally express the antibody κ light chain. For example, antibodies or oligonucleotides can be used to identify cells or tissues that naturally express the antibody κ light chain of the present invention.

[0027] Alternatively, the antibody κ light chain according to the present invention can be chemically synthesized. The method of chemical synthesis is not particularly limited, and any method used for chemically synthesizing polypeptides may be used.

[0028] The production method according to the first embodiment of the present invention may further include other steps such as a purification step. The purification step may be carried out appropriately using a known antibody purification method, but for example, a purification method consisting of a first purification step, an addition step, and a second purification step, which will be described later, may also be used. These steps will be described in detail below.

[0029] [Second embodiment] The method for producing an antibody κ-type light chain according to the second embodiment of the present invention (hereinafter sometimes abbreviated as "the production method according to the second embodiment of the present invention") comprises the following steps in this order: an expression step of expressing the antibody κ light chain in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain; a first purification step of obtaining a crude product containing the antibody κ light chain from the expression product obtained in the expression step by column chromatography using a column containing a first packing material; an adding step of adding a metal ion to the crude product containing the antibody κ light chain to obtain a crude product containing an antibody κ light chain complex in which the antibody κ light chain and the metal ion are bound; a second purification step of obtaining a purified product of the antibody-κ light chain complex from the crude product containing the antibody-κ light chain complex after the adding step by column chromatography using a column containing a second packing material; a removal step of removing the metal ions from the purified antibody κ light chain complex product after the second purification step to obtain a purified antibody κ light chain product.

[0030] The production method according to the second embodiment of the present invention is not limited to antibody κ light chains that are polypeptides whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or contains an amino acid residue other than proline, but can also be applied to other antibody κ light chains. The production method according to the second embodiment of the present invention enables the stable production of antibody enzymes with excellent storage stability. Each step will be described in detail below.

[0031] <Expression process> In the expression step, an expression vector containing a polynucleotide encoding the antibody κ light chain is used to express the antibody κ light chain using an expression system known in the technical field, such as an intracellular or extracellular expression system.

[0032] When a recombinant expression system is used, a polynucleotide encoding the antibody κ-type light chain of the present invention can be incorporated into a recombinant expression vector, which is then introduced into a host capable of expression by a known method, and the polypeptide obtained by translation in the host (transformant) can be purified. The recombinant expression vector may or may not be a plasmid, as long as it is capable of introducing the target polynucleotide into the host.

[0033] When introducing a foreign polynucleotide into a host in this manner, it is preferable that the expression vector incorporates a promoter that functions in the host to express the foreign polynucleotide. Methods for purifying recombinantly produced polypeptides vary depending on the host used and the properties of the polypeptide, but the use of tags, etc. makes it relatively easy to purify the target polypeptide.

[0034] When a cell-free expression system (cell-free protein synthesis system) is used, it is preferable to add a polynucleotide encoding the antibody κ light chain of the present invention to a solution containing components necessary for protein translation and synthesis, such as ribosomes and t-RNA, and incubate the solution at an appropriate temperature to purify the synthesized polypeptide.

[0035] Examples of cell-free protein synthesis systems include systems using wheat germ extract, systems using rabbit reticulocyte extract, systems using Escherichia coli S30 extract, and systems using extracts of cellular components obtained from devacuolated plant protoplasts. Generally, eukaryotic systems, i.e., systems using wheat germ extract or rabbit reticulocyte extract, are selected for translation of eukaryotic genes. However, any of the above synthesis systems may be selected taking into consideration the origin of the gene to be translated (prokaryote / eukaryote) and the intended use of the protein after synthesis. Various commercially available kits can be used as these synthesis systems.

[0036] Since many virus-derived gene products express their activity after translation through complex biochemical reactions involving intracellular membranes such as the endoplasmic reticulum and Golgi apparatus, the addition of intracellular membrane components (e.g., microsomal membranes) is necessary to reproduce various biochemical reactions in a test tube. Extracts of cellular components obtained from devacuolated plant protoplasts are preferred because they can be used as cell-free protein synthesis solutions that retain intracellular membrane components and do not require the addition of microsomal membranes.

[0037] As used herein, the term "intracellular membrane component" refers to organelles composed of lipid membranes present in the cytoplasm (i.e., intracellular granules in general, such as the endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, and vacuoles). In particular, the endoplasmic reticulum and Golgi apparatus play important roles in post-translational modification of proteins, and are essential cellular components for the maturation of membrane proteins and secretory proteins.

[0038] The antibody κ light chain of the present invention can also be isolated from cells or tissues that naturally express the antibody κ light chain. For example, antibodies or oligonucleotides can be used to identify cells or tissues that naturally express the antibody κ light chain of the present invention.

[0039] Alternatively, the antibody κ light chain according to the present invention can be chemically synthesized. The method of chemical synthesis is not particularly limited, and any method used for chemically synthesizing polypeptides may be used.

[0040] <First purification step> In the first purification step, a crude product containing the antibody κ light chain is obtained from the expression product obtained in the expression step by column chromatography using a column containing a first packing material.

[0041] A preferred method for purifying the antibody κ-type light chain from the expression product obtained in the expression step is to prepare a cell extract from the cells or tissues by a well-known method (e.g., a method in which cells or tissues are disrupted and then centrifuged to collect a soluble fraction), and then purify the cell extract by a well-known method (e.g., ammonium sulfate precipitation or ethanol precipitation, acid extraction, anion or cation exchange chromatography, phosphocellulose chromatography, hydrophobic interaction chromatography, affinity chromatography, hydroxyapatite chromatography, and lectin chromatography), but this method is not limited to these. Most preferably, high performance liquid chromatography ("HPLC") is used for purification.

[0042] <Addition process> In the addition step, a metal ion is added to the crude composition containing the antibody κ light chain to obtain a crude composition containing an antibody κ light chain complex in which the antibody κ light chain and the metal ion are bound. By adding the metal ion to the crude composition containing the antibody κ light chain, antibody κ light chain dimers can be easily obtained and can be stably produced while maintaining the enzymatic activity of the antibody κ light chain.

[0043] In the present invention, the metal ion bound to the antibody κ light chain is one or more selected from the group consisting of Group 10 elements, Group 11 elements, and Group 12 elements. Only one type of metal ion may be bound to the antibody κ light chain, or two or more types may be bound in combination. From the viewpoint of safety to living organisms, the metal ion is preferably one or more selected from the group consisting of copper ions, nickel ions, zinc ions, gold ions, silver ions, and platinum ions. From the viewpoint of mass productivity, the metal ion is more preferably one or more selected from the group consisting of copper ions, nickel ions, and zinc ions. From the viewpoint of further enhancing the activity of the antibody κ light chain in living organisms, copper ions are even more preferred.

[0044] Examples of methods for adding metal ions to a crude composition containing an antibody κ light chain include incubating the antibody κ light chain of the present invention in a solution containing the metal ions. The antibody κ light chain may be incubated with metal ions in a solution containing a mixture of antibody κ light chain dimers and monomers, or an antibody κ light chain purified to contain only one of the dimers or monomers may be incubated with metal ions.

[0045] The incubation time of the antibody κ light chain of the present invention with the metal ions can be appropriately determined taking into consideration the type of antibody κ light chain, the type of metal ion, the solvent, the incubation temperature, etc., so that a sufficient amount of metal ions can bind to the antibody κ light chain. For example, it is preferable to incubate the antibody κ light chain at room temperature for 30 minutes to 48 hours, and then subject the mixture to the subsequent second purification step.

[0046] <Second purification step> In the second purification step, a purified product of the antibody-κ light chain complex is obtained from the crude product containing the antibody-κ light chain complex after the adding step by column chromatography using a column containing a second packing material.

[0047] The method for purifying the purified antibody-κ light chain complex from the crude antibody-κ light chain complex-containing product in the second purification step includes the same methods as those exemplified in the first purification step, and most preferably, high performance liquid chromatography ("HPLC") is used for purification.

[0048] The combination of the first packing material in the first purification step and the second packing material in the second purification step is not particularly limited, as long as it allows for the final purification of the antibody κ light chain to the desired degree of purity, and can be appropriately determined taking into account the type of antibody κ light chain, the presence or absence of additions or modifications, etc. For example, when the antibody κ light chain synthesized using an expression system is an epitope-tagged polypeptide with a His tag or the like, it is preferable to use a packing material with high affinity for the labeled epitope as the first packing material, and to use anion or cation exchange chromatography as the second packing material. In this case, the antibody κ light chain is purified in the first purification step, and then in the second purification step, the monomer and dimer can be separated and fractionated, or fractionated based on the presence or absence of metal ion binding.

[0049] <Removal process> In the removal step, the metal ions are removed from the purified antibody κ light chain complex product obtained after the second purification step to obtain a purified antibody κ light chain product. Removal of metal ions from the purified antibody κ light chain complex product can improve the storage stability of the antibody κ light chain, as shown in the Examples below.

[0050] Examples of methods for removing the metal ions from the purified antibody-κ light chain complex include a method in which the purified antibody-κ light chain complex is incubated in a solution containing a chelating agent.

[0051] Examples of the chelating agent used in the removal step include ethylenediaminetetraacetic acid (EDTA), citric acid, and phytic acid.

[0052] The manufacturing method according to the second embodiment of the present invention may include other steps in addition to the steps described above. For example, when the production method according to the second embodiment of the present invention is used to produce an antibody κ light chain that is a polypeptide in which the variable region is an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue, the production method may further include a modification step.

[0053] <Modification process> In the modification step, prior to the expression step, a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, is modified so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue.

[0054] The method for modifying the polypeptide so as to delete or substitute the proline residue can be carried out by using well-known techniques to easily mutate the proline residue located at position 95 from the N-terminus of the variable region according to the Kabat classification in the amino acid sequence of the variable region, among the amino acid residues constituting the polypeptide. For example, any base in a polynucleotide encoding the polypeptide can be mutated according to known point mutagenesis methods. Alternatively, a deletion mutant or substitution mutant can be prepared by designing a primer corresponding to any site in a polynucleotide encoding the polypeptide.

[0055] <Antibody κ light chain> The antibody κ light chain of the present invention is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or contains an amino acid residue other than proline. The antibody κ light chain of the present invention is an antibody enzyme and has higher enzymatic activity than conventional antibody enzymes. That is, the antibody enzyme of the present invention consists of an antibody κ light chain that is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or contains an amino acid residue other than proline, and expresses enzymatic activity using a recognized antigen as a substrate. The antibody κ light chain of the present invention can be produced by the above-mentioned "method for producing an antibody κ light chain."

[0056] Hereinafter, the antibody κ light chain of the present invention may be referred to as a "proline-deleted variant." As used herein, a proline-deleted variant refers to a peptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is not a proline residue, and may be one in which the corresponding proline residue in a wild-type antibody κ light chain is deleted, or one in which the proline residue is substituted with another amino acid residue.

[0057] Numbering of amino acid sequences according to the Kabat classification can be performed, for example, by analyzing the amino acid sequence of an antibody according to the Kabat numbering system using abYsis software (URL: http: / / www.abysis.org / ).

[0058] The antibody κ light chain of the present invention is not particularly limited as long as it has the above-described structure. However, from the viewpoint of applicability to pharmaceutical applications, it is preferable that it has a catalytic triad-like structure. The catalytic triad-like structure is, for example, a structure formed by serine, histidine, and asparagine residues and is thought to have catalytic activity. Examples of antibody κ light chains having a catalytic triad-like structure include those having a Vκ gene belonging to subgroup II, those having a Vκ gene belonging to other subgroups such as subgroup I, those having at least the variable regions thereof, and mutants thereof. Wild-type antibody κ light chains can be obtained by PCR or the like using nucleic acids derived from human biological samples (e.g., lymphocytes) as a template, as disclosed in Patent Document 2, for example. Furthermore, various mutants can be obtained from the obtained wild-type antibody by known gene recombination techniques.

[0059] The antibody κ light chain of the present invention preferably has at least one of protease activity, amidase activity, nucleolytic activity, cytotoxicity against cancer cells, and antiviral activity, and is particularly useful as an anticancer agent, antiviral agent, etc.

[0060] Wild-type antibody κ light chains contain cysteines for forming disulfide bonds and form dimers. Mutant antibody κ light chains in which the cysteines are substituted with other amino acids (e.g., alanine) cannot form dimers and exist as monomers. The antibody κ light chains of the present invention may be either monomeric or dimeric. However, depending on the type of antibody κ light chain, dimers may have higher protease activity and other activities than monomers, and in such cases, dimeric light chains are preferred.

[0061] The antibody κ-type light chain (proline-deleted) according to the present invention preferably has a variable region that is a polypeptide selected from the group consisting of the following (1a) to (3c): (1a) a polypeptide consisting of an amino acid sequence in which the proline residue at the 100th position from the N-terminus (the 95th position from the N-terminus of the variable region according to the Kabat classification) in the amino acid sequence represented by SEQ ID NO: 1 has been deleted or substituted; (1b) A polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (1a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (1c) A polypeptide having an amino acid sequence that has 90% or more identity with the amino acid sequence of the polypeptide of (1a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (2a) an amino acid sequence in which the proline residue at the 100th position from the N-terminus (the 95th position from the N-terminus of the variable region according to the Kabat classification) in the amino acid sequence represented by SEQ ID NO: 2 has been deleted or substituted; (2b) A polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (2a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (2c) A polypeptide having an amino acid sequence that has 90% or more identity with the amino acid sequence of the polypeptide of (2a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (3a) an amino acid sequence in which the proline residue at the 100th position from the N-terminus (the 95th position from the N-terminus of the variable region according to the Kabat classification) in the amino acid sequence represented by SEQ ID NO: 3 has been deleted or substituted; (3b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (3a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (3c) A polypeptide having an amino acid sequence that has 90% or more identity with the amino acid sequence of the polypeptide of (3a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue.

[0062] In the polypeptides (1a) to (3c) above, the amino acid residue that can be substituted for the proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification is not particularly limited, as long as it has a side chain that is less bulky than a proline residue and does not interfere with the formation of the catalytic triad-like structure. Examples of such amino acid residues include lysine, arginine, histidine, aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, alanine, glycine, valine, isoleucine, leucine, methionine, and cysteine. Among these, serine and arginine are preferred.

[0063] Furthermore, the sequence identity of a subject amino acid sequence to a reference amino acid sequence can be determined, for example, as follows: First, the reference amino acid sequence and the subject amino acid sequence are aligned. Here, gaps may be included in each amino acid sequence to maximize sequence identity. Next, the number of matching amino acids in the reference amino acid sequence and the subject amino acid sequence is calculated, and the sequence identity can be determined according to the following formula.

[0064] "Sequence identity (%)" = [number of matching amino acids] / [total number of amino acids in the target amino acid sequence] x 100

[0065] A human antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 1, is sometimes referred to as a "human antibody κ light chain (S35)." The human antibody κ light chain (S35) may have a known human antibody constant region added to the variable region, and in one embodiment, its full-length amino acid sequence is set forth in SEQ ID NO: 10. In the human antibody κ light chain (S35), CDR1 is located at positions 24 to 39 in the amino acid sequence of SEQ ID NOs: 1 and 10, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 1 and 10, and CDR3 is located at positions 94 to 102 in the amino acid sequence of SEQ ID NOs: 1 and 10. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 219 in the amino acid sequence of SEQ ID NO: 10.

[0066] As shown in the Examples below, human antibody κ light chain (S35) does not have the activity of degrading an antigen peptide consisting of the amino acid sequence from the 26th to the 33rd amino acid from the N-terminus of amyloid β (hereinafter, sometimes referred to as "Aβ peptide"). However, a human antibody κ light chain having a variable region consisting of an amino acid sequence represented by SEQ ID NO: 1 in which the proline residue at the 95th position from the N-terminus according to the Kabat classification has been deleted or substituted, i.e., a human antibody κ light chain whose variable region is the polypeptide (1a) above (hereinafter, sometimes referred to as "proline-deleted human antibody κ light chain (S35)"), can exhibit the activity of degrading Aβ peptide. Therefore, it is suitable as an active ingredient of an anti-amyloid β (Aβ) degrading agent. For the anti-Aβ degrading activity of the proline-deleted human antibody κ light chain (S35), high molecular recognition ability for target molecules is important. Therefore, the active center of the anti-Aβ degrading activity of the proline-deleted human antibody κ light chain (S35) is located in the variable region, particularly the CDR sequence.

[0067] The proline-deleted mutant of the human antibody κ-type light chain (S35) may be a mutant with a mutation that does not impair enzymatic activity. Among these, the proline-deleted mutant of the human antibody κ-type light chain (S35) is preferably a mutant with a mutation in a region other than the variable region, and more preferably a mutant in which CDR1 and CDR2 are identical (conserved) to the amino acid sequence set forth in SEQ ID NO: 1 or 10, a C-terminal proline residue in CDR3 is deleted or substituted, while the other amino acid sequences in CDR3 are identical (conserved), and amino acids in the variable region other than the CDR region may be mutated from those in the human antibody κ-type light chain (S35). Examples of the proline-deleted mutant of the human antibody κ-type light chain (S35) include human antibody κ-type light chains whose variable region is the polypeptide of (1b) or (1c) above.

[0068] In the polypeptide of (1b) above, the number of amino acids that may be deleted, substituted, or added is preferably from 1 to 5, more preferably from 1 to 2, and even more preferably 1. The same applies hereinafter to proline-deleted mutants whose variable regions are polypeptides such as (2b) or (3b) above.

[0069] Commonly occurring amino acid substitutions include, for example, alanine / serine, valine / isoleucine, aspartic acid / glutamic acid, threonine / serine, alanine / glycine, alanine / threonine, serine / asparagine, alanine / valine, serine / glycine, tyrosine / phenylalanine, alanine / proline, lysine / arginine, aspartic acid / asparagine, leucine / isoleucine, leucine / valine, alanine / glutamic acid, and aspartic acid / glycine.

[0070] In order for the polypeptide of (1c) above to be functionally equivalent to the polypeptide consisting of the amino acid sequence of (1a) above, it must be a polypeptide that, like the polypeptide of (1a) above, does not have a proline residue at position 95 from the N-terminus of the variable region in the amino acid sequence represented by SEQ ID NO: 1 according to the Kabat classification, and whose amino acid sequence is 90% or more identical to the amino acid sequence of the polypeptide of (1a) above, preferably 95% or more identical, more preferably 97% or more identical, and even more preferably 99% or more identical. The same applies hereinafter to proline-deleted mutants whose variable region is a polypeptide of (2c) or (3c) above.

[0071] Furthermore, examples of proline-deleted mutants of the human antibody κ-type light chain (S35) include polypeptides represented by the amino acid sequence of SEQ ID NO: 10 in which the proline residue at position 95 is deleted and the cysteine ​​at position 219 is replaced with alanine.

[0072] A human antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 2, is sometimes referred to as a "human antibody κ light chain (T99)." The human antibody κ light chain (T99) may have a known human antibody constant region added to the variable region, and in one embodiment, its full-length amino acid sequence is set forth in SEQ ID NO: 13. In the human antibody κ light chain (T99), CDR1 is located at positions 24 to 39 in the amino acid sequence of SEQ ID NOs: 2 and 13, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 2 and 13, and CDR3 is located at positions 94 to 102 in the amino acid sequence of SEQ ID NOs: 2 and 13. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 219 in the amino acid sequence of SEQ ID NO: 13.

[0073] As shown in the Examples below, human antibody κ light chain (T99) does not have the activity of degrading Aβ peptides. However, a human antibody κ light chain having a variable region consisting of an amino acid sequence in which the proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 2 has been deleted or substituted, i.e., a human antibody κ light chain whose variable region is the polypeptide described in (2a) above (hereinafter, sometimes referred to as a "proline-deleted human antibody κ light chain (T99)") can exhibit the activity of degrading Aβ peptides. Therefore, it is suitable as an active ingredient of an anti-Aβ degrading agent. For the anti-Aβ degrading activity of the proline-deleted human antibody κ light chain (T99), high molecular recognition ability for target molecules is important. Therefore, the active center of the anti-amyloid β degrading activity of the proline-deleted human antibody κ light chain (T99) is located in the variable region, particularly the CDR sequence.

[0074] The proline-deleted human antibody κ light chain (T99) may be a mutant with a mutation that does not impair enzymatic activity. Among these, proline-deleted mutants of the human antibody κ light chain (T99) are preferably mutants with a mutation in a region other than the variable region, and more preferably mutants in which CDR1 and CDR2 are identical (conserved) to the amino acid sequence set forth in SEQ ID NO: 2 or 13, a C-terminal proline residue in CDR3 is deleted or substituted, while the other amino acid sequences in CDR3 are identical (conserved), and amino acids in the variable region other than the CDR region may be mutated from those in the human antibody κ light chain (T99). Examples of proline-deleted mutants of the human antibody κ light chain (T99) include human antibody κ light chains whose variable region is the polypeptide described in (2b) or (2c) above.

[0075] Furthermore, examples of proline-deleted mutants of the human antibody κ-type light chain (T99) include polypeptides represented by the amino acid sequence of SEQ ID NO: 13 in which the proline residue at position 95 is deleted and the cysteine ​​at position 219 is replaced with alanine.

[0076] A human antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 3, is sometimes referred to as a "human antibody κ light chain (H55)." The human antibody κ light chain (H55) may have a known human antibody constant region added to the variable region, and in one embodiment, its full-length amino acid sequence is set forth in SEQ ID NO: 15. In the human antibody κ light chain (H55), CDR1 is located at positions 24 to 39 in the amino acid sequence of SEQ ID NOs: 3 and 15, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 3 and 15, and CDR3 is located at positions 94 to 103 in the amino acid sequence of SEQ ID NOs: 3 and 15. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 215 in the amino acid sequence of SEQ ID NO: 15.

[0077] As shown in the Examples below, human antibody κ light chain (H55) does not have the activity to degrade an antigen peptide consisting of the amino acid sequence from amino acids 124 to 141 from the N-terminus of PD-1, an immune checkpoint receptor present on the surface of cytotoxic T cells (hereinafter, sometimes referred to as "PD-1 peptide"). However, a human antibody κ light chain having a variable region consisting of an amino acid sequence represented by SEQ ID NO: 3 in which the proline residue at position 95 from the N-terminus according to the Kabat classification has been deleted or substituted (hereinafter, sometimes referred to as "proline-deleted human antibody κ light chain (H55)") can degrade PD-1 peptide. Therefore, it is suitable as an active ingredient of an anticancer agent. For the anticancer activity of the proline-deleted human antibody κ light chain (H55), high molecular recognition ability for target molecules is important. Therefore, the active center of the anticancer activity of the proline-deleted human antibody κ light chain (H55) is located in the variable region, particularly the CDR sequence.

[0078] The proline-deleted variant of the human antibody κ light chain (H55) may be a variant with a mutation that does not impair enzymatic activity. Among these, the proline-deleted variant of the human antibody κ light chain (H55) is preferably a variant with a mutation in a region other than the variable region, and more preferably a variant in which CDR1 and CDR2 are identical (conserved) to the amino acid sequence set forth in SEQ ID NO: 3 or 15, a proline residue at the C-terminus of CDR3 is deleted or substituted, while the other amino acid sequences of CDR3 are identical (conserved), and amino acids in the variable region other than the CDR region may be mutated from those of the human antibody κ light chain (H55). Examples of the proline-deleted variant of the human antibody κ light chain (H55) include human antibody κ light chains whose variable region is the polypeptide of (3b) or (3c) above.

[0079] Furthermore, examples of proline-deleted mutants of the human antibody κ-type light chain (H55) include polypeptides represented by the amino acid sequence of SEQ ID NO: 15 in which the proline residue at position 95 is deleted and the cysteine ​​at position 215 is replaced with alanine.

[0080] The antibody κ-type light chain (proline-deleted) according to the present invention is more preferably a polypeptide whose variable region is selected from the group consisting of the following (4a) to (7c): (4a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 4; (4b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 4, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (4c) a polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 4 and consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (5a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 5; (5b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 5, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (5c) a polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 5 and having a deletion or an amino acid residue other than a proline residue at the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification; (6a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 6; (6b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 6, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (6c) A polypeptide having 90% or more identity to the amino acid sequence represented by SEQ ID NO: 6 and consisting of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (7a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 7; (7b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 7, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (7c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 7, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue.

[0081] A human antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 4, may also be referred to as a "human antibody κ light chain (S34)." A human antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 5, may also be referred to as a "human antibody κ light chain (S38)." The human antibody κ light chain (S34) and the human antibody κ light chain (S38) are proline-deleted forms of the human antibody κ light chain (S35). In one embodiment, the full-length amino acid sequence of the human antibody κ light chain (S34) is set forth in SEQ ID NO: 11, and the full-length amino acid sequence of the human antibody κ light chain (S38) is set forth in SEQ ID NO: 12.

[0082] In the human antibody κ-type light chain (S34), CDR1 is located at positions 24 to 39 in the amino acid sequence of SEQ ID NOs: 4 and 11, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 4 and 11, and CDR3 is located at positions 94 to 104 in the amino acid sequence of SEQ ID NOs: 4 and 11. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 219 in the amino acid sequence of SEQ ID NO: 11.

[0083] In the human antibody κ-type light chain (S38), CDR1 is located at positions 24 to 39 in the amino acid sequence of SEQ ID NOs: 5 and 12, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 5 and 12, and CDR3 is located at positions 94 to 103 in the amino acid sequence of SEQ ID NOs: 5 and 12. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 218 in the amino acid sequence of SEQ ID NO: 12.

[0084] The human antibody κ light chain (S34) and the human antibody κ light chain (S38) may be mutants with mutations that do not impair enzymatic activity. Among these, the human antibody κ light chain (S34) mutants and the human antibody κ light chain (S38) mutants are preferably mutants with mutations in regions other than the variable region, and more preferably mutants in which CDR1, CDR2, and CDR3 are identical (conserved) to the amino acid sequences set forth in SEQ ID NOs: 4, 5, 11, or 12 and amino acids in the variable region other than the CDR regions may be mutated from the human antibody κ light chain (S34) and the human antibody κ light chain (S38). Examples of human antibody κ light chain (S34) mutants include human antibody κ light chains whose variable region is the polypeptide of (4b) or (4c) above. Examples of human antibody κ light chain (S38) mutants include human antibody κ light chains whose variable region is the polypeptide of (5b) or (5c) above.

[0085] A human antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 6, is sometimes referred to as "human antibody κ light chain (T99 P95Δ)." The human antibody κ light chain (T99 P95Δ) is a proline-deleted form of the human antibody κ light chain (T99). In one embodiment, the full-length amino acid sequence of the human antibody κ light chain (T99 P95Δ) is set forth in SEQ ID NO: 14. In the human antibody κ light chain (T99 P95Δ), CDR1 is located at positions 24 to 39 in the amino acid sequence of SEQ ID NOs: 6 and 14, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 6 and 14, and CDR3 is located at positions 94 to 103 in the amino acid sequence of SEQ ID NOs: 6 and 14. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 218 in the amino acid sequence of SEQ ID NO: 14.

[0086] The human antibody κ light chain (T99 P95Δ) may be a mutant having mutations that do not impair enzymatic activity. Among these, the human antibody κ light chain (T99 P95Δ) mutant is preferably a mutant having mutations in regions other than the variable region, and more preferably a mutant in which CDR1, CDR2, and CDR3 are identical to (conserved) the amino acid sequence set forth in SEQ ID NO: 6 or 14 and amino acids in the variable region other than the CDR regions may be mutated from the human antibody κ light chain (T99 P95Δ). Examples of human antibody κ light chain (T99 P95Δ) mutants include human antibody κ light chains whose variable region is the polypeptide of (6b) or (6c) above.

[0087] A human antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 7, is sometimes referred to as a "human antibody κ light chain (H34)." The human antibody κ light chain (H34) is a proline-deleted form of the human antibody κ light chain (H55). In one embodiment, the full-length amino acid sequence of the human antibody κ light chain (H34) is set forth in SEQ ID NO: 16. In the human antibody κ light chain (H34), CDR1 is located at positions 24 to 39 in the amino acid sequence of SEQ ID NOs: 7 and 16, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 7 and 16, and CDR3 is located at positions 94 to 101 in the amino acid sequence of SEQ ID NOs: 7 and 16. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 213 in the amino acid sequence of SEQ ID NO: 16.

[0088] The human antibody κ light chain (H34) may be a mutant having a mutation that does not impair enzymatic activity. Among these, the human antibody κ light chain (H34) mutant is preferably a mutant having a mutation in a region other than the variable region, and more preferably a mutant in which CDR1, CDR2, and CDR3 are identical to (conserved) the amino acid sequence set forth in SEQ ID NO: 7 or 16, and in which amino acids in the variable region other than the CDR region may be mutated from the human antibody κ light chain (H34). Examples of the human antibody κ light chain (H34) mutant include a human antibody κ light chain whose variable region is the polypeptide of (7b) or (7c) above.

[0089] Furthermore, the antibody κ-type light chain (proline-deleted) according to the present invention preferably has a variable region that is a polypeptide selected from the group consisting of the following (8a) to (8c): (8a) an amino acid sequence in which the proline residue at the 100th position from the N-terminus (the 95th position from the N-terminus of the variable region according to the Kabat classification) in the amino acid sequence represented by SEQ ID NO: 8 has been deleted or substituted; (8b) A polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence of the polypeptide of (8a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (8c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence of the polypeptide of (8a) above, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue.

[0090] A mouse antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 8, is sometimes referred to as a "mouse antibody κ light chain (InfA-15L)." The mouse antibody κ light chain (InfA-15L) may have a known human antibody constant region added to the variable region, and in one embodiment, its full-length amino acid sequence is set forth in SEQ ID NO: 17. In the mouse antibody κ light chain (InfA-15L), CDR1 is located at positions 21 to 39 in the amino acid sequence of SEQ ID NOs: 8 and 17, CDR2 is located at positions 55 to 61 in the amino acid sequence of SEQ ID NOs: 8 and 17, and CDR3 is located at positions 94 to 102 in the amino acid sequence of SEQ ID NOs: 8 and 17. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 219 in the amino acid sequence of SEQ ID NO: 17.

[0091] As shown in the Examples below, mouse antibody κ light chain (InfA-15L) does not have the decomposition activity for a substrate consisting of benzoyl group (Bz group)-D / L-arginine-paranitroaniline (pNA) (hereinafter, sometimes referred to as "trypsin-like pNA (R-pNA)"). However, a human antibody κ light chain having a variable region consisting of an amino acid sequence represented by SEQ ID NO: 8 in which the proline residue at position 95 from the N-terminus according to the Kabat classification has been deleted or substituted, i.e., a mouse antibody κ light chain whose variable region is the polypeptide (8a) above (hereinafter, sometimes referred to as "proline-deleted mouse antibody κ light chain (InfA-15L)"), can exhibit decomposition activity for R-pNA. Therefore, it can be used as a trypsin-like enzyme. For the trypsin-like enzyme activity of the proline-deleted mouse antibody kappa light chain (InfA-15L), high molecular recognition ability for target molecules is important. Therefore, the active center of the trypsin-like enzyme activity of the proline-deleted mouse antibody kappa light chain (InfA-15L) is located in the variable region, particularly the CDR sequence.

[0092] The proline-deleted mutant of the mouse antibody κ light chain (InfA-15L) may be a mutant with a mutation that does not impair enzymatic activity. Among these, a mutant with a mutation in a region other than the variable region is preferred as the proline-deleted mutant of the mouse antibody κ light chain (InfA-15L). This mutant has CDR1 and CDR2 identical (conserved) to the amino acid sequence set forth in SEQ ID NO: 8 or 17, at least one of the second and third proline residues from the C-terminus of CDR3 is deleted or substituted, while the other amino acid sequences of CDR3 are identical (conserved), and amino acids in the variable region other than the CDR region may be mutated from the mouse antibody κ light chain (InfA-15L). Examples of proline-deleted mutants of the mouse antibody κ light chain (InfA-15L) include mouse antibody κ light chains whose variable region is the polypeptide described in (8b) or (8c) above.

[0093] Furthermore, examples of proline-deleted mutants of the mouse antibody κ-type light chain (InfA-15L) include polypeptides represented by the amino acid sequence of SEQ ID NO: 17 in which the proline residue at position 95 is deleted and the cysteine ​​at position 219 is replaced with alanine.

[0094] The antibody κ-type light chain (proline-deleted) according to the present invention preferably has a variable region that is a polypeptide selected from the group consisting of the following (9a) to (9c): (9a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 9; (9b) a polypeptide consisting of an amino acid sequence in which one or several amino acids are substituted, added, or deleted in the amino acid sequence represented by SEQ ID NO: 9, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (9c) A polypeptide having an amino acid sequence having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 9, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue.

[0095] A mouse antibody κ light chain, which is a polypeptide whose variable region consists of the amino acid sequence set forth in SEQ ID NO: 9, is sometimes referred to as "mouse antibody κ light chain (InfA-15L P95Δ)." The mouse antibody κ light chain (InfA-15L P95Δ) is a proline-deleted version of the mouse antibody κ light chain (InfA-15L). In one embodiment, the full-length amino acid sequence of the mouse antibody κ light chain (InfA-15L P95Δ) is set forth in SEQ ID NO: 18. In the mouse antibody κ light chain (InfA-15L P95Δ), CDR1 corresponds to positions 21 to 39 in the amino acid sequence set forth in SEQ ID NOs: 9 and 18, CDR2 corresponds to positions 55 to 61 in the amino acid sequence set forth in SEQ ID NOs: 9 and 18, and CDR3 corresponds to positions 94 to 101 in the amino acid sequence set forth in SEQ ID NOs: 9 and 18. The cysteine ​​that forms a disulfide bond with another light chain is the cysteine ​​at position 218 in the amino acid sequence of SEQ ID NO:18.

[0096] The mouse antibody κ light chain (InfA-15L P95Δ) may be a mutant having mutations that do not impair enzymatic activity. Among these, preferred mutants of the mouse antibody κ light chain (InfA-15L P95Δ) are those having mutations in regions other than the variable region, and more preferred are mutants in which CDR1, CDR2, and CDR3 are identical (conserved) to the amino acid sequences set forth in SEQ ID NO: 9 or 18, and in which amino acids in the variable region other than the CDR regions may be mutated from those of the mouse antibody κ light chain (InfA-15L P95Δ). Examples of mutants of the mouse antibody κ light chain (InfA-15L P95Δ) include human antibody κ light chains whose variable region is the polypeptide described in (9b) or (9c) above.

[0097] Furthermore, the antibody κ light chain of the present invention is not limited to the above-mentioned examples. For example, by deleting or substituting the proline residue at the 95th position from the N-terminus of the variable region of a known antibody κ light chain according to the Kabat classification, it is possible to express enzymatic activity while maintaining antigen recognition ability.

[0098] Furthermore, the antibody κ light chain of the present invention may contain an additional polypeptide, such as an epitope-tagged polypeptide tagged with His tag, Myc tag, or Flag tag.

[0099] Those skilled in the art can easily mutate one or several amino acids among the amino acid residues constituting a polypeptide, or add an epitope-tagged polypeptide, using well-known techniques. For example, any base in a polynucleotide encoding a polypeptide can be mutated according to known point mutagenesis methods. Furthermore, deletion or addition mutants can be prepared by designing primers corresponding to any site in a polynucleotide encoding a polypeptide.

[0100] The antibody κ light chains of the present invention include naturally occurring purified products, products of chemical synthesis procedures, and products produced by recombinant techniques from prokaryotic or eukaryotic hosts (including, for example, bacterial cells, yeast cells, higher plant cells, insect cells, and mammalian cells). Depending on the host used in a recombinant production procedure, the antibody κ light chains of the present invention may be glycosylated or non-glycosylated. Furthermore, the antibody κ light chains of the present invention may also contain a modified initial methionine residue, in some cases as a result of host-mediated processes.

[0101] The antibody κ light chain of the present invention may be, but is not limited to, a polypeptide in which amino acids are peptide-bonded, and may also be a complex polypeptide containing a structure other than a polypeptide. As used herein, "structure other than a polypeptide" includes, but is not limited to, a sugar chain, an isoprenoid group, and the like.

[0102] <Pharmaceutical composition> The antibody κ light chain according to the present invention is particularly suitable for use as a pharmaceutical composition for anticancer agents, antiviral agents, amyloid β degrading agents, and the like.

[0103] The anticancer agent of the present invention (anticancer agent containing the antibody κ light chain of the present invention as an active ingredient) can be administered by direct injection for use in humans or animals. The anticancer agent of the present invention can also be formulated for parenteral, mucosal, intramuscular, intravenous, subcutaneous, intraocular, or transdermal administration. Typically, the protein contained in the composition can be administered at a dose of 0.01 to 30 mg / kg body weight, preferably 0.1 to 10 mg / kg body weight, and more preferably 0.1 to 1 mg / kg body weight.

[0104] The anti-cancer agent of the present invention may contain, in addition to the antibody κ-type light chain of the present invention, a pharmaceutically acceptable carrier, diluent, or excipient (including a combination thereof). Pharmaceutically acceptable carriers and excipients for therapeutic use are well known in the pharmaceutical field and are described, for example, in Remington's Pharmaceutical Sciences, Mack Publishing Co. (A.R. Gennaro, ed., 1985). The selection of a pharmaceutically acceptable carrier, excipient, or diluent can be easily selected by one skilled in the art according to the intended route of administration and standard pharmaceutical practice. The anti-cancer agent of the present invention may further contain any suitable binder, lubricant, suspending agent, coating agent, or solubilizing agent.

[0105] Depending on the different delivery systems, the composition / formulation requirements may differ. For example, the anticancer agent of the present invention may be formulated for delivery using a minipump or via a mucosal route, e.g., as a nasal spray or aerosol for inhalation, or parenterally (where the anticancer agent of the present invention is formulated as an injectable form for delivery via, e.g., intravenous, intramuscular, or subcutaneous routes). Alternatively, the formulation may be designed for delivery via both routes. Other preferred forms include a nasal spray or aerosol for inhalation, which allows for efficient delivery from the nose, bronchi, etc. to lung cells.

[0106] Furthermore, when the anticancer agent of the present invention is administered in vivo, various techniques can be used to improve the in vivo stability (serum half-life) of the antibody κ light chain, which is the active ingredient. For example, it is known that binding of neonatal Fc receptor (FcRn) to Fc extends the serum half-life of antibodies such as IgG (see, for example, Roopenian, DC et al., Nat Rev Immunol vol. 7 pp. 715-725 (2007)). The C-terminus of the antibody κ light chain of the present invention can be modified to have FcRn-binding activity. Furthermore, the antibody κ light chain of the present invention can be dimerized or PEG (polyethylene glycol) can be attached.

[0107] The anticancer agent according to the present invention can also be packaged as a kit together with, for example, instructions on how to take the agent, etc. The kit can also contain various other medicines that can be used in combination with the anticancer agent according to the present invention.

[0108] Furthermore, since the anticancer agent of the present invention contains as an active ingredient an antibody κ light chain that has a high ability to recognize target molecules, it does not exhibit cytotoxicity against cancer cells that do not have the target molecule of the antibody κ light chain present on their cell surface, and is therefore expected to be useful in identifying types of cancer. [Example]

[0109] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0110] [Construction of an expression system for human antibody κ light chain] In the following examples, the following were used: a human antibody κ light chain (S35) consisting of the amino acid sequence of SEQ ID NO: 10, a human antibody κ light chain (T99) consisting of the amino acid sequence of SEQ ID NO: 13, a human antibody κ light chain (H55) consisting of the amino acid sequence of SEQ ID NO: 15, a human antibody κ light chain (S34) consisting of the amino acid sequence of SEQ ID NO: 11, a human antibody κ light chain (S38) consisting of the amino acid sequence of SEQ ID NO: 12, a human antibody κ light chain (T99 P95Δ) consisting of the amino acid sequence of SEQ ID NO: 14, a human antibody κ light chain (H34) consisting of the amino acid sequence of SEQ ID NO: 16, a mouse antibody κ light chain (InfA-15L) consisting of the amino acid sequence of SEQ ID NO: 17, a mouse antibody κ light chain (InfA-15L P95Δ) consisting of the amino acid sequence of SEQ ID NO: 18, and a human antibody κ light chain (#7_wt) consisting of the amino acid sequence of SEQ ID NO: 19. These human antibody κ light chains were banked human antibody κ light chains produced by B lymphocytes.

[0111] These human antibody κ light chains were each expressed in an E. coli expression system. Specifically, cDNAs encoding each human antibody κ light chain were inserted into a plasmid vector containing a His tag sequence, and the plasmid vector was then introduced into E. coli to produce transformants. Each transformant was cultured and expression was induced with IPTG. SDS-PAGE analysis and Western blotting using anti-human (Fab')2 antibody confirmed that the protein expressed in E. coli was a human antibody light chain. The resulting human antibody light chain contained M (methionine) at the N-terminus and LEHHHHHH (SEQ ID NO: 20) derived from the plasmid vector at the C-terminus.

[0112] [Expression and purification of human antibody κ-type light chain] Human antibody κ-type light chains that had not been treated with metal ions or had metal ions removed were expressed and purified as follows.

[0113] First, the E. coli transformant containing the expression vector prepared above was cultured overnight in LB medium at 37°C, and then IPTG was added to the culture to a final concentration of 10 μM (μmol / L), followed by overnight culture at 18°C. After completion of the culture, the cells were collected from the culture by centrifugation, and sodium chloride-containing Tris buffer (25 mM Tris-HCl, 0.25 M NaCl, pH 8.0) was added to the collected cells. The cells were disrupted by sonication, and then centrifuged to collect the soluble fraction.

[0114] Next, in the first purification step, this soluble fraction was applied to a Ni-NTA column (Qiagen) packed with Ni-NTA agarose, and an appropriate amount of the sodium chloride-containing Tris buffer was passed through the Ni-NTA column to adsorb the expressed human antibody κ light chain to the Ni-NTA column. The human antibody κ light chain was then eluted from the Ni-NTA column using an imidazole-containing Tris buffer (25 mM Tris-HCl, 0.25 M NaCl, imidazole, pH 8.0) with a gradient of imidazole concentrations from 0.03 M to 0.3 M, and a fraction containing the human antibody κ light chain was isolated. The recovered human antibody κ light chain-containing fraction was dialyzed against acetate buffer (50 mM acetic acid, pH 5.5) at 4°C for 12 to 24 hours.

[0115] In the second purification step, the dialyzed human antibody κ light chain-containing fraction was applied to a cation exchange column (product number: SP-5PW, manufactured by TOSOH Corporation), and an appropriate amount of the acetate buffer was passed through the cation exchange column to adsorb the expressed human antibody κ light chain to the cation exchange column. The human antibody κ light chain was then eluted from the cation exchange column using either a sodium chloride-containing acetate buffer (50 mM acetic acid, NaCl, pH 5.5) with a sodium chloride gradient from 0.15 M to 0.45 M or a sodium chloride-containing Tris-HCl buffer (pH 8.0) with a sodium chloride gradient from 0.0 w / v% to 15.0 w / v%, and the human antibody κ light chain-containing fraction was isolated. Alternatively, size exclusion chromatography (HiLoad column) was used instead of the cation exchange column. TM 16 / 60 Superdex TM The purified product was purified using 200 pg (GE Healthcare) of PBS (pH 7.4) as the elution solvent. The collected fraction containing human antibody κ light chain was dialyzed against sodium chloride-containing Tris buffer (20 mM Tris-HCl, 0.15 M NaCl, pH 8.5) at 4°C for 12 to 24 hours, and then further dialyzed against PBS (pH 7.4) at 4°C for 12 to 24 hours. The dialyzed fraction was used as human antibody κ light chain.

[0116] [Evaluation of enzyme activity] The enzymatic activity of each human antibody κ light chain was evaluated using an assay system that uses the FRET peptide shown in the following structural formula as a substrate. In the structural formula, "MCA" represents a 7-methoxycoumarin-4-methylamide structure, "DNP" represents a 2,4-dinitrophenyl group, "Lys" represents a lysine residue, and "D-Arg" represents a D-arginine residue.

[0117] MCA-(antigen peptide)-Lys(DNP)-(D-Arg)3

[0118] The types and sequences of antigen peptides are shown in Table 1 below. In Table 1, "Aβ" stands for amyloid beta, and "Tau" stands for tau protein, both of which are causative agents of dementia. "PD-1" is an immune checkpoint molecule. In each case, the number in parentheses indicates the position from the N-terminus of the full-length amino acid sequence, and partial peptides were used. In addition, in the amino acid sequence of tau protein, "pS" stands for a phosphorylated serine residue.

[0119] [Table 1]

[0120] The human antibody κ light chain and the FRET substrate were added to 100 μL of PBS (pH 7.4) to a final concentration of 5 μM and 100 μM, respectively, and incubated at 37°C for up to 120 hours. The time-dependent change in the concentration of p-nitroaniline (dominant wavelength 405 nm, minor wavelength 620 nm) due to substrate cleavage was measured.

[0121] [Example 1] Using a human antibody κ-type light chain (#7_wt), the effect of adding copper ions in the purification process and then removing the copper ions on the storage stability of the human antibody κ-type light chain was examined.

[0122] Specifically, human antibody κ light chain (#7_wt) was obtained by a preparation method (Case 1) similar to that described in [Expression and Purification of Human Antibody κ Light Chain] above, except that, in the control case, copper ions were added to the eluate from Ni-NTA column purification to a final concentration of 15 μM, incubated at 4°C for 12 to 16 hours, and then dialyzed against the acetate buffer. Furthermore, the eluate from cation exchange column purification was dialyzed against the sodium chloride-containing Tris buffer containing ethylenediaminetetraacetic acid (EDTA) to a final concentration of 50 mM, followed by dialysis against PBS. The resulting human antibody κ light chain (#7_wt) was stored at 4°C for 3 months.

[0123] [Comparative Example 1] Human antibody κ light chain (#7_wt) was obtained by a preparation method (Case 2) similar to that described in [Expression and Purification of Human Antibody κ Light Chain] above, except that in the control case, copper ions were added to the eluate after Ni-NTA column purification to a final concentration of 15 μM, and the mixture was incubated at 4°C for 12 to 16 hours before dialysis against the acetate buffer. The resulting human antibody κ light chain (#7_wt) was stored at 4°C for 3 days or 3 months.

[0124] Figure 1A shows the cation exchange chromatogram (UV (280 nm) absorbance (mAU) of the eluate at each retention time and the sodium chloride concentration (M) of the eluate) for the control case (no copper ions added), and Figure 1B shows the results of SDS-PAGE (non-reducing) of fractions 1 to 3 shown in Figure 1A. Fraction 1 contained only the human antibody κ light chain (#7_wt) monomer, while fraction 2 contained both monomer and dimer, with the monomer predominating. Fraction 3 mainly contained dimer.

[0125] Figure 2A shows the cation exchange chromatogram for Case 1 (copper ions added after primary purification and removed after secondary purification). Figure 2B shows the SDS-PAGE (non-reducing) results for Fraction 1A shown in Figure 2A. Figure 2C shows the cation exchange chromatogram for Case 1 after 3 months of storage at 4°C. In Case 1, a single large peak was observed at a position corresponding to Fraction 3 in the control case. The SDS-PAGE results indicated that the human antibody κ light chain (#7_wt) contained in Fraction 1A was almost entirely dimerized. Purification in the presence of copper ions confirmed that dimerization was more likely than monomer formation. Furthermore, even after 3 months of storage at 4°C, a single large peak was observed at a position corresponding to Fraction 3 in the control case. These results demonstrate that removal of copper ions enables stable long-term storage.

[0126] Figure 3A shows the cation exchange chromatogram for Case 2 (copper ions added after primary purification), and Figure 3B shows the results of SDS-PAGE (non-reducing) of fractions 1B and 2B shown in Figure 3A. In Case 2, immediately after purification, one large peak was observed at a position corresponding to fraction 3 in the control case. However, storage at 4°C for 3 days and 3 months showed a tendency for the number of peaks to increase over time. Since the increased peaks were also dimers, it was inferred that the presence of copper ions had destabilized the structure of some of the dimers.

[0127] [Example 2] The degradation activity against Aβ peptide was evaluated using human antibody κ light chain (S35), human antibody κ light chain (S34), and human antibody κ light chain (S38). Specifically, human antibody κ light chain (S35), human antibody κ light chain (S34), and human antibody κ light chain (S38) were obtained using the same method as in Case 1 of Example 1. Next, the degradation activity of each human antibody κ light chain against Aβ peptide was evaluated using the same method as in the above "Evaluation of enzymatic activity" except that the FRET substrate concentration was set to 25 μM.

[0128] Figure 4A is a graph showing the time course of the FRET-Aβ peptide degradation activity of human antibody κ light chain (S35), human antibody κ light chain (S34), and human antibody κ light chain (S38). For human antibody κ light chain (S34) and human antibody κ light chain (S38), the fluorescence intensity increased over time, demonstrating Aβ peptide degradation activity. In contrast, for human antibody κ light chain (S35), almost no fluorescence was detected, demonstrating no Aβ peptide degradation activity.

[0129] Figure 4B shows the amino acid sequences of the variable regions of the human antibody κ light chain (S35), human antibody κ light chain (S34), and human antibody κ light chain (S38). In Figure 4B, 2 / 2D-28*01 is one of the light chains encoded by the V gene of subgroup II present on the fertilized egg chromosome. The amino acid sequences (SEQ ID NO: 24) of the portions corresponding to the variable regions of the human antibody κ light chain (S35), human antibody κ light chain (S34), and human antibody κ light chain (S38) are shown. Furthermore, "-" indicates the same amino acid residue as 2 / 2D-28*01. Comparison of the amino acid sequences reveals that the human antibody κ light chain (S35) has a proline residue at the 95th position from the N-terminus of the variable region according to the Kabat classification, whereas the human antibody κ light chain (S38) lacks this proline residue, and the proline residue is replaced with a serine residue in the human antibody κ light chain (S34). It was speculated that the activity of the antibody enzyme would be significantly improved by deleting or substituting this proline residue.

[0130] [Example 3] We investigated the effect of the presence or absence of a proline residue at position 95 from the N-terminus of the variable region on the activity of antibody enzymes. Specifically, we evaluated the Aβ peptide degradation activity using a human antibody kappa light chain (T99), a clone with a proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification, and a human antibody kappa light chain (T99 P95Δ) in which the proline residue at position 95 from the N-terminus of the variable region of the human antibody kappa light chain (T99) was deleted according to the Kabat classification.

[0131] Specifically, a human antibody κ light chain (T99) and a human antibody κ light chain (T99 P95Δ) were obtained using the same method as in Case 1 of Example 1. Next, the degradation activity of each human antibody κ light chain against Aβ peptide was evaluated using the same method as in the above "Evaluation of enzymatic activity."

[0132] Figure 5A is a graph showing the time course of the FRET-Aβ peptide degradation activity of human antibody κ light chain (T99) and human antibody κ light chain (T99 P95Δ). The fluorescence intensity of the human antibody κ light chain (T99 P95Δ) increased over time, demonstrating its Aβ peptide degradation activity. In contrast, almost no fluorescence was detected in the human antibody κ light chain (T99), demonstrating no Aβ peptide degradation activity.

[0133] Figure 5B shows the predicted three-dimensional structures of the variable regions of the human antibody kappa light chain (T99) and human antibody kappa light chain (T99 P95Δ). In Figure 5B, "S27a" represents the serine residue at position 27a from the N-terminus of the variable region, "H27d" represents the histidine residue at position 27d from the N-terminus of the variable region, "H93" represents the histidine residue at position 93 from the N-terminus of the variable region, "P95" represents the proline residue at position 95 from the N-terminus of the variable region, and "D1" represents the aspartic acid residue at position 1 from the N-terminus of the variable region. Deletion of the proline residue at position 95 from the N-terminus of the variable region significantly altered the distance between the amino acid residues constituting the enzyme active site (catalytic triad-like structure) (the distance between H93 and D1 in Figure 5B).

[0134] Similar to the human antibody κ light chain (T99), the human antibody κ light chain (S35) has been confirmed to have a catalytic triad-like structure, as shown in Figure 5B. Many subgroup II Vκ genes are thought to have this catalytic triad-like structure, but not all κ light chains produced from these genes exhibit enzymatic activity. However, it has been suggested that deleting the proline residue at position 95 from the N-terminus of the variable region (according to the Kabat classification) or substituting it with an amino acid residue with a more compact structure than a proline residue can alter the catalytic triad-like structure to an appropriate position, thereby conferring peptidase activity to antibodies.

[0135] [Example 4] For clones derived from subgroup I Vκ genes, we investigated the effect of the presence or absence of a proline residue at position 95 from the N-terminus of the variable region (Kabat classification) on antibody enzyme activity. Specifically, we evaluated the PD-1 peptide degradation activity using a human antibody κ light chain (H55), a clone with a proline residue at position 95 from the N-terminus (Kabat classification) in the variable region, and a human antibody κ light chain (H34), a clone with a variable region amino acid sequence that does not have a proline residue at position 95 from the N-terminus (Kabat classification).

[0136] Specifically, human antibody κ light chain (H55) and human antibody κ light chain (H34) were obtained using the same method as in Case 1 of Example 1. Next, the decomposition activity of each human antibody κ light chain against PD-1 peptide was evaluated using the same method as in the above "Evaluation of enzymatic activity."

[0137] Figure 6A is a graph showing the time course of the degradation activity of human antibody κ light chain (H55) and human antibody κ light chain (H34) toward FRET-PD-1 peptide. The fluorescence intensity of human antibody κ light chain (H34) increased over time, indicating its degradation activity toward PD-1 peptide. In contrast, almost no fluorescence was detected in human antibody κ light chain (H55), indicating no degradation activity toward PD-1 peptide.

[0138] Figure 6B shows the amino acid sequences of the variable regions of the human antibody κ light chain (H55) and the human antibody κ light chain (H34). In Figure 6B, 1-39*01 and 1-5*03 are light chains encoded by subgroup I V genes present on fertilized egg chromosomes, respectively. The amino acid sequences (SEQ ID NOS: 25 and 26) corresponding to the variable regions of the human antibody κ light chain (H55) and the human antibody κ light chain (H34) are shown. Furthermore, "-" indicates the same amino acid residue as 1-39*01 for the human antibody κ light chain (H55) and the same amino acid residue as 1-5*03 for the human antibody κ light chain (H34). Comparison of the amino acid sequences reveals that the human antibody κ light chain (H55) has a proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification, whereas this proline residue is replaced with an arginine residue in the human antibody κ light chain (H34). From this, it was speculated that deletion or substitution of this proline residue would also significantly improve the activity of antibody enzymes in clones derived from subgroup I Vκ genes.

[0139] To investigate the substrate specificity of the human antibody κ light chain (H34), the decomposition activity of Aβ peptide, tau peptide, and PD-1 peptide was evaluated using the same method as described above in [Evaluation of enzymatic activity].

[0140] Figure 6C is a graph showing the time course of the degradation activity of human antibody κ light chain (H34) toward FRET-Aβ peptide, FRET-Tau peptide, and FRET-PD-1 peptide. The degradation activity of human antibody κ light chain (H34) toward PD-1 peptide was observed, but the degradation activity toward FRET-Aβ peptide and FRET-Tau peptide was not observed. This demonstrates that human antibody κ light chain (H34) specifically recognizes and degrades PD-1 peptide.

[0141] To identify the degradation site of the PD-1 peptide by the human antibody kappa light chain (H34), the solution after the above degradation test was analyzed by high-performance liquid chromatography (HPLC), and the peaks that appeared were collected and analyzed by mass spectrometry (MS). The measurement conditions are shown below.

[0142] (HPLC conditions) Equipment: Waters Delta 600, Waters 2489 UV / Visible Detector (Waters) Column: Cosmosil type, 5C18-AR-2 (4.6 x 250 mm), Nacalai Mobile phase: Phase A (MilliQ water in 0.05% TFA), Phase B (Acetonitrile in 0.05% TFA) Gradient:90%A phase to 40% A phase in 50min(1% / min) Flow rate: 1.0 mL / min Detection: 220nm

[0143] (MS conditions) Device: microTOF-Q (Bruker Daltonics)

[0144] Figure 6D shows the HPLC analysis of the PD-1 peptide after degradation by the human antibody kappa light chain (H34). The degradation site of the PD-1 peptide was determined to be the peptide bond between Q (glutamine) and I (isoleucine).

[0145] Furthermore, the degradation activity of the human antibody κ light chain (H34) toward full-length recombinant human PD-1 was evaluated using the same method as described above in "Evaluation of enzyme activity," except that full-length recombinant human PD-1 was used as the substrate and human serum albumin (HSA) was used as the control substrate.

[0146] The results of SDS-PAGE (non-reducing) of each solution after the degradation test are shown in Figure 6E. Degradation fragments of PD-1 were confirmed at the sites indicated by arrows, demonstrating the degrading activity of the human antibody κ light chain (H34) against full-length recombinant human PD-1.

[0147] Furthermore, to evaluate the effect on enzyme activity of the presence or absence of a proline residue at the 95th position from the N-terminus of the variable region of the human antibody κ light chain (H34) according to the Kabat classification, a mutant (hereinafter sometimes referred to as "human antibody κ light chain (H34_P95(+))" (SEQ ID NO: 27) in which a proline residue was inserted at the 95th position from the N-terminus of the variable region of the human antibody κ light chain (H34) according to the Kabat classification was prepared.

[0148] Specifically, a human antibody κ light chain (H34) and a human antibody κ light chain (H34_P95(+)) were obtained using a method similar to that used in Case 1 of Example 1. Next, the decomposition activity of each human antibody κ light chain against PD-1 peptide was evaluated using a method similar to that described above in "Evaluation of enzymatic activity."

[0149] Figure 6F is a graph showing the time course of the degradation activity of the human antibody κ light chain (H34) and human antibody κ light chain (H34_P95(+)) toward the FRET-PD-1 peptide. The fluorescence intensity of the human antibody κ light chain (H34) increased over time, indicating its degradation activity toward the PD-1 peptide. In contrast, the human antibody κ light chain (H34_P95(+)) showed almost no fluorescence, indicating no degradation activity toward the PD-1 peptide. This confirms that the activity of the antibody enzyme varies depending on the presence or absence of a proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification.

[0150] These results suggest that the enzymatic activity may be elicited not only from antibody κ light chains derived from Vκ genes of subgroup II, but also from antibody κ light chains derived from Vκ genes of other subgroups, by deleting or substituting the proline residue at the 95th position from the N-terminus according to the Kabat classification in the amino acid sequence of the variable region.

[0151] [Example 5] We investigated the effect of the presence or absence of a proline residue at position 95 from the N-terminus of the variable region (Kabat classification) on the activity of antibody enzymes derived from mouse Vκ gene clones. Specifically, we evaluated trypsin-like paranitroaniline (R-pNA) degradation activity using mouse antibody κ light chain (InfA-15L), a clone with a proline residue at position 95 from the N-terminus (Kabat classification) in the variable region, and mouse antibody κ light chain (InfA-15L P95Δ), a clone lacking the proline residue at position 95 from the N-terminus (Kabat classification) in the variable region. R-pNA is a substrate with the following structure. Hydrolysis of the peptide bond between arginine and pNA results in pNA dissociation and fluorescence detection.

[0152] R-pNA: Benzoyl group (Bz group)-D / L-arginine-pNA

[0153] Specifically, a mouse antibody κ light chain (InfA-15L) and a mouse antibody κ light chain (InfA-15L P95Δ) were obtained using a method similar to that used in Case 1 of Example 1. Next, the R-pNA decomposition activity of each human antibody κ light chain was evaluated using a method similar to that described above in "Evaluation of enzyme activity," except that R-pNA was used as the substrate.

[0154] Figure 7 is a graph showing the time course of the R-pNA degradation activity of mouse antibody κ light chain (InfA-15L) and mouse antibody κ light chain (InfA-15L P95Δ). The fluorescence intensity of the mouse antibody κ light chain (InfA-15L P95Δ) increased over time, indicating its R-pNA degradation activity. In contrast, almost no fluorescence was detected in the mouse antibody κ light chain (InfA-15L), indicating no R-pNA degradation activity. This suggests that, similar to the human antibody κ light chain, the activity of the antibody enzyme in the mouse antibody κ light chain is significantly improved by deleting the proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification. [Industrial Applicability]

[0155] The present invention can be used in the fields of manufacturing pharmaceuticals containing a human antibody κ light chain as an active ingredient, the development of new anticancer agents, cancer treatment, and dementia treatment.

Claims

1. A method for producing an antibody κ light chain having enzymatic activity or improved enzymatic activity, comprising the steps of: a modification step of modifying a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue; an expression step of expressing the antibody κ light chain having enzymatic activity in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain after the modification step; Including, the variable region of the antibody κ light chain having enzymatic activity or improved enzymatic activity is a polypeptide selected from the group consisting of the following (1a), (1c), (2a), (2c), (3a), and (3c): When the variable region of the antibody κ light chain having enzymatic activity or improved enzymatic activity is a polypeptide of the following (1a), (1c), (2a), or (2c), the enzymatic activity is Aβ-degrading activity: When the variable region of the antibody κ-type light chain having enzymatic activity or improved enzymatic activity is a polypeptide of the following (3a) or (3c), the enzymatic activity is PD-1 degradation activity. (1a) a polypeptide consisting of an amino acid sequence in which the proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 1 is deleted or substituted; (1c) A polypeptide having an amino acid sequence in which amino acids in regions other than the 24th to 39th, 55th to 61st, and 94th to 102nd amino acid residues in the amino acid sequence of the polypeptide of (1a) are substituted, added, or deleted, and having 90% or more identity with the amino acid sequence of the polypeptide of (1a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (2a) a polypeptide consisting of an amino acid sequence in which the proline residue at position 95 from the N-terminus of the variable region according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 2 is deleted or substituted; (2c) A polypeptide having an amino acid sequence in which amino acids in regions other than the 24th to 39th, 55th to 61st, and 94th to 102nd amino acid residues in the amino acid sequence of the polypeptide of (2a) are substituted, added, or deleted, and having an identity of 90% or more with the amino acid sequence of the polypeptide of (2a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (3a) a polypeptide consisting of an amino acid sequence in which the 95th proline residue from the N-terminus of the variable region according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 3 is deleted or substituted; (3c) A polypeptide in which amino acids in the region other than the 24th to 39th, 55th to 61st, and 94th to 103rd amino acid residues of the amino acid sequence of the polypeptide of (3a) are substituted, added, or deleted, and which has 90% or more identity with the amino acid sequence of the polypeptide of (3a), and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue.

2. A method for producing an antibody κ light chain having enzymatic activity or improved enzymatic activity, comprising the steps of: a modification step of modifying a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue; an expression step of expressing the antibody κ light chain having enzymatic activity in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain after the modification step; Including, the variable region of the antibody κ light chain having enzymatic activity or improved enzymatic activity is a polypeptide selected from the group consisting of the following (4a), (4c), (5a), (5c), (6a), (6c), (7a), and (7c), When the variable region of the antibody κ light chain having the enzymatic activity or the enzymatic activity improved is a polypeptide of the following (4a), (4c), (5a), (5c), (6a), or (6c), the enzymatic activity is Aβ degrading activity, When the variable region of the antibody κ-type light chain having enzymatic activity or improved enzymatic activity is a polypeptide of the following (7a) or (7c), the enzymatic activity is PD-1 degradation activity. (4a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 4; (4c) A polypeptide consisting of an amino acid sequence in which amino acids in a region other than the 24th to 39th, 55th to 61st, and 94th to 104th amino acid residues of the amino acid sequence represented by SEQ ID NO: 4 are substituted, added, or deleted, and which has 90% or more identity with the amino acid sequence represented by SEQ ID NO: 4, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (5a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 5; (5c) A polypeptide consisting of an amino acid sequence in which amino acids in a region other than the 24th to 39th, 55th to 61st, and 94th to 103rd amino acid residues of the amino acid sequence represented by SEQ ID NO: 5 are substituted, added, or deleted, and which has 90% or more identity with the amino acid sequence represented by SEQ ID NO: 5, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (6a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 6; (6c) A polypeptide consisting of an amino acid sequence in which amino acids in a region other than the 24th to 39th, 55th to 61st, and 94th to 103rd amino acid residues of the amino acid sequence represented by SEQ ID NO: 6 are substituted, added, or deleted, and which has 90% or more identity with the amino acid sequence represented by SEQ ID NO: 6, and in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or is an amino acid residue other than a proline residue; (7a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 7; (7c) A polypeptide consisting of an amino acid sequence in which amino acids in a region other than the 24th to 39th, 55th to 61st, and 94th to 101st amino acid residues of the amino acid sequence represented by SEQ ID NO: 7 are substituted, added, or deleted, and has 90% or more identity with the amino acid sequence represented by SEQ ID NO: 7, and in which the 95th amino acid residue from the N-terminus of the variable region in the Kabat classification is deleted or is an amino acid residue other than a proline residue.

3. A method for producing an antibody κ light chain having enzymatic activity or improved enzymatic activity, comprising the steps of: a modification step of modifying a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue; an expression step of expressing the antibody κ light chain having enzymatic activity in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain after the modification step; Including, the enzyme activity is trypsin-like coenzyme activity, The method of claim 1, wherein the variable region of the antibody κ light chain having enzymatic activity or improved enzymatic activity is a polypeptide selected from the group consisting of the following (8a) and (8c): (8a) a polypeptide consisting of an amino acid sequence in which the 95th proline residue from the N-terminus of the variable region according to the Kabat classification in the amino acid sequence represented by SEQ ID NO: 8 is deleted or substituted; (8c) The amino acid sequence of the polypeptide of (8a) has substitutions, additions, or deletions of amino acids in regions other than the 21st to 39th, 55th to 61st, and 94th to 102nd amino acid residues, and has 90% or more identity with the amino acid sequence of the polypeptide of (8a), and the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification. A polypeptide consisting of an amino acid sequence in which the amino acid residue is deleted or is an amino acid residue other than a proline residue.

4. A method for producing an antibody κ light chain having enzymatic activity or improved enzymatic activity, comprising the steps of: a modification step of modifying a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is a proline residue, so that the proline residue is deleted or substituted, thereby obtaining a polynucleotide encoding an antibody κ light chain, which is a polypeptide whose variable region consists of an amino acid sequence in which the 95th amino acid residue from the N-terminus of the variable region according to the Kabat classification is deleted or has an amino acid residue other than a proline residue; an expression step of expressing the antibody κ light chain having enzymatic activity in an intracellular or extracellular expression system using an expression vector comprising a polynucleotide encoding the antibody κ light chain after the modification step; Including, the enzyme activity is trypsin-like coenzyme activity, The method for producing the antibody κ light chain variable region having enzymatic activity or improved enzymatic activity, wherein the variable region is a polypeptide selected from the group consisting of (9a) and (9c) below: (9a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 9; (9c) A polypeptide consisting of an amino acid sequence in which amino acids in a region other than the 21st to 39th, 55th to 61st, and 94th to 101st amino acid residues of the amino acid sequence represented by SEQ ID NO: 9 are substituted, added, or deleted, and has 90% or more identity with the amino acid sequence represented by SEQ ID NO: 9, and in which the 95th amino acid residue from the N-terminus of the variable region in the Kabat classification is deleted or is an amino acid residue other than a proline residue.

5. The method according to any one of claims 1 to 4, wherein the antibody κ light chain is human or mouse.

6. An antibody kappa light chain, the variable region of which is a polypeptide selected from the group consisting of (6a) and (6c) below. (6a) a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 6; (6c) A polypeptide having Aβ decomposition activity, in which amino acids in a region other than the 24th to 39th, 55th to 61st, and 94th to 103rd amino acid residues of the amino acid sequence represented by SEQ ID NO: 6 are substituted, added, or deleted, and having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 6, and in which the 95th amino acid residue from the N-terminus of the variable region in the Kabat classification is deleted or is an amino acid residue other than a proline residue.

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