PmST3 Sialyltransferase Substrate Promiscuity E. coli Expression
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Solution Overview
Problem
Mammalian glycosyltransferases, including sialyltransferases, face challenges with low expression and restricted substrate specificity in E. coli systems, limiting their application in synthesizing glycoconjugates, whereas bacterial glycosyltransferases are more accessible but lack enzymes with wide substrate tolerance.
Innovation Solution
The development of a method using the sialyltransferase PmST3 and its variants for synthesizing glycosylated molecules by forming a reaction mixture with an acceptor molecule, a donor substrate containing a sugar moiety and a nucleotide, under conditions that transfer the sugar moiety from the donor to the acceptor, along with the use of a CMP-sialic acid synthetase and sialic acid aldolase for in situ synthesis of CMP-sialic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mammalian glycosyltransferases are used for synthesis, then substrate specificity is improved, but expression level and ease of manufacture deteriorate
Solution Approach 1:
The patent uses E. coli expression systems to produce bacterial glycosyltransferases that replicate the functional characteristics of mammalian enzymes. By cloning bacterial sialyltransferase genes into E. coli expression vectors, the patent creates a system that maintains substrate specificity while achieving high expression levels, effectively copying the useful traits of mammalian enzymes without their expression limitations.
Solution Approach 2:
The patent modifies expression parameters by using inducible promoters (such as lac promoter), controlling temperature conditions, and adjusting media composition to optimize protein expression. These parameter changes enable high-level expression of glycosyltransferases in E. coli, resolving the contradiction between expression level and substrate specificity.
2Ease of manufacture
If bacterial glycosyltransferases are used for synthesis, then ease of manufacture is improved, but substrate tolerance is worsened
Solution Approach 1:
The patent identifies and utilizes bacterial glycosyltransferases that exhibit promiscuous substrate specificity, allowing a single enzyme to accept multiple substrates. For example, certain bacterial sialyltransferases can accept both natural and analog substrates, expanding substrate tolerance while maintaining ease of manufacture through E. coli expression systems.
Solution Approach 2:
The patent employs mutagenesis and directed evolution to modify bacterial glycosyltransferases, changing their substrate binding parameters to enhance tolerance. By introducing specific amino acid mutations, the enzymes gain the ability to accept a broader range of substrates while retaining their ease of expression in E. coli.
3Adaptability or versatility
If wild-type bacterial glycosyltransferases are used, then substrate flexibility is improved, but enzyme reliability for specific synthesis deteriorates
Solution Approach 1:
The patent applies localized mutations at specific positions in the enzyme active site to fine-tune substrate recognition. By making targeted changes at critical residues while maintaining the overall enzyme structure and expression capabilities, the patent achieves both substrate flexibility and synthesis reliability for specific applications.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the high-yield production of sialic acid-containing molecules with improved substrate promiscuity, allowing for the synthesis of various oligosaccharides, glycopeptides, glycoproteins, and glycolipids, enhancing the application of glycosyltransferases in biological and pathological processes.
Implementation Method 1
Glycosyltransferase-catalyzed reactions have gained increasing attention and application for the synthesis of complex carbohydrates and glycoconjugates. Sialyltransferases, in particular, are the key enzymes that catalyze the transfer of a sialic acid residue from cytidine 5′-monophosphate-sialic acid (CMP-sialic acid) to an acceptor.
Implementation Method 2
the donor substrate is formed via conversion of a suitable hexosamine derivative to a cytidine 5′-monophosphate(CMP)-sialic acid in a one-pot reaction mixture containing a sialic acid aldolase and a CMP-sialic acid synthetase
Data Source
AI summary
The present invention provides novel methods for preparing glycosylated molecules such as oligosaccharides, glycolipids, and glycoproteins/peptides. Novel sialyltransferases are also disclosed. The method includes forming a reaction mixture containing an acceptor molecule, a donor substrate having a sugar moiety and a nucleotide, and a sialyltransferase selected from PmST3 (SEQ ID NO:7) and certain variants thereof. The reaction mixture is formed under conditions sufficient to transfer the sugar moiety from the donor substrate to the acceptor molecule, thereby forming the glycosylated molecule. In some embodiments, the acceptor molecule is selected from a natural product, an oligosaccharide, a glycoprotein, and a glycolipid. In some embodiments, the donor substrate is formed via conversion of a suitable hexosamine derivative to a cytidine 5′-monophosphate(CMP)-sialic acid in a one-pot reaction mixture containing asialic acid aldolase and a CMP-sialic acid synthetase.