Xanthine oxidase inhibiting peptide and its engineering method and application

Abstract

The application discloses a xanthine oxidase inhibiting peptide and a modification method and application thereof, and has the characteristics that the amino acid sequence of the inhibiting peptide is KEAKER and / or KNAKNR, the modification method comprises the following steps: (1) all dipeptides obtained by combining common amino acids in pairs are used as ligands, xanthine oxidase is used as a receptor, and a molecular docking module of Discovery Studio software is used to score molecular docking interaction between the dipeptides and the xanthine oxidase; (2) a natural active peptide with xanthine oxidase inhibiting activity is used as a template, and dominant dipeptides with high scoring values are used to replace inferior dipeptides with low scoring values in the natural active peptide, so that the xanthine oxidase inhibiting peptide with improved inhibiting activity is obtained; and the advantage is that the xanthine oxidase inhibiting activity can be quickly and effectively improved without changing the length of the active peptide chain and affecting the bioavailability.

Description

Technical Field

[0001] This invention relates to the field of polypeptide technology, and in particular to a xanthine oxidase inhibitory peptide, its modification method, and its application. Background Technology

[0002] Increased uric acid synthesis or decreased uric acid excretion in the body leads to elevated blood uric acid levels, resulting in hyperuricemia. Hyperuricemia is the second leading metabolic disease worldwide, characterized by high serum uric acid levels and is a major risk factor for gout, kidney damage, and metabolic syndrome. Treatment for hyperuricemia primarily involves increasing uric acid excretion and inhibiting uric acid production. Purine metabolism is the main source of uric acid in the human body. Purines come from two sources: endogenous nucleotide metabolism and exogenous purine-rich foods metabolized into uric acid in the intestines. Endogenous nucleotides (adenine nucleotides and guanine nucleotides) undergo a series of biochemical reactions to ultimately produce uric acid. Adenine nucleotides are catalyzed by nucleotidase, nucleoside deaminase, and nucleoside phosphorylase to produce hypoxanthine, which is then catalyzed twice by xanthine oxidase to finally produce uric acid. Guanine is catalyzed by guanine deaminase to produce xanthine, which is then catalyzed by xanthine oxidase to produce uric acid. Xanthine oxidase is considered an important inhibitory target in the uric acid production pathway.

[0003] Bioactive peptides are multifunctional compounds derived from natural proteins, ranging from dipeptides to polypeptides. It has been reported that many mixed oligopeptides with the ability to alleviate hyperuricemia have been discovered in natural bioactive proteins. Using the molecular docking module in Discovery Studio, xanthine oxidase can be docked with oligopeptides, enabling efficient screening of active peptides within mixed peptides. Both peptide chain structure and amino acid sequence affect the inhibitory effect of xanthine oxidase. Existing methods to enhance the xanthine oxidase inhibitory activity of bioactive peptides include sequentially removing amino acids from the N-terminus and sequentially adding amino acids from one end. However, altering the peptide chain length can affect the bioavailability of bioactive peptides to some extent. Currently, there are no published research reports, domestically or internationally, on improving the xanthine oxidase inhibition rate by altering the amino acid structure of the peptide chain without changing the peptide chain length. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a xanthine oxidase inhibitory peptide with xanthine oxidase activity and uric acid-lowering activity, as well as its modification method and application. The modification method can rapidly and effectively improve xanthine oxidase inhibitory activity without changing the length of the active peptide chain or affecting its bioavailability.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a xanthine oxidase inhibitory peptide, wherein the amino acid sequence of the inhibitory peptide is: KEAKER and / or KNAKNR.

[0006] The method for modifying the above-mentioned xanthine oxidase inhibitory peptide includes the following steps: (1) All dipeptides obtained by combining common amino acids in pairs were used as ligands, and xanthine oxidase was used as the acceptor. The molecular docking interaction between the dipeptides and xanthine oxidase was assigned using the molecular docking module of Discovery Studio software. (2) Using a natural active peptide with xanthine oxidase inhibitory activity as a template, replace the inferior dipeptide with a low score in the natural active peptide with the superior dipeptide with a high score obtained in step (1) to obtain a xanthine oxidase inhibitory peptide with improved inhibitory activity.

[0007] Furthermore, the common amino acids mentioned include glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, and histidine.

[0008] The above-mentioned xanthine oxidase inhibitory peptide is used in the preparation of xanthine oxidase activity inhibitors.

[0009] The above-mentioned xanthine oxidase inhibitory peptides are used in the preparation of uric acid-lowering drugs or adjunctive treatment drugs for gout.

[0010] Compared with the prior art, the advantages of the present invention are as follows: The present invention provides a xanthine oxidase inhibitory peptide, its modification method and application, which, through software prediction, in vitro enzyme activity inhibition experiments, cell modeling experiments and animal model experiments, can quickly and accurately screen and evaluate the xanthine oxidase inhibitory activity of different dipeptide units. By replacing the inferior dipeptide elements in the original active peptide with the screened superior dipeptide elements, the xanthine oxidase inhibitory activity of the active peptide can be successfully improved. Without changing the length of the active peptide chain or affecting its bioavailability, it can quickly and effectively enhance the inhibitory or enhancing effect of bioactive peptides on target proteins and can be applied to the targeted modification of natural active peptides. Attached Figure Description

[0011] Figure 1 To predict the interaction between dipeptides and xanthine oxidase based on molecular docking and to validate the in vitro enzyme activity inhibition function. A. Simulate the interaction between dipeptides and xanthine oxidase using the molecular docking module of Discovery Studio software; B. Quantitatively assign scores to the interactions between 400 dipeptides and xanthine oxidase; C. In vitro xanthine oxidase activity inhibition results of 10 dipeptides; D. Correlation analysis between the software-based quantitative scoring prediction and the actual in vitro enzyme activity inhibition ability; Figure 2To evaluate the uric acid-lowering function of the dipeptide at the cellular level. A. Effect of allopurinol on cell viability; B. Uric acid-lowering activity of allopurinol at the cellular level; C. Effect of the dipeptide on cell viability; D. Uric acid-lowering activity of the dipeptide at the cellular level; Figure 3 This study investigates the effect of dipeptides on the expression of proteins related to the uric acid metabolism pathway at the cellular level. A. Expression of proteins related to the uric acid synthesis pathway at the cellular level; B. Expression of proteins related to the uric acid excretion and reabsorption pathways at the cellular level. Figure 4 Evaluation of the dipeptide's uric acid-lowering function in mice. A. Serum uric acid concentration; B. Serum xanthine oxidase activity; Figure 5 This study focuses on the targeted modification of bioactive peptides and the evaluation of their effects. A. Schematic diagram of the targeted modification strategy for hexapeptide GPAGPR; B. Comparison of the in vitro XOD enzyme activity inhibitory activity of the bioactive peptides (40 mg / ml) before and after modification. Detailed Implementation

[0012] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Specific Implementation Example 1 Twenty common amino acids, including glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, and histidine, were selected and combined in pairs to obtain 400 dipeptides (the C-terminus and N-terminus of amino acids are different dipeptides) as ligands. Xanthine oxidase (XOD, PDB database number: 1FIQ), an important target in the uric acid production pathway, was selected as the receptor for molecular docking-based interaction assignment. Figure 1 As shown in Figure A, the interaction between the dipeptide and xanthine oxidase was simulated using the molecular docking module of Discovery Studio software. The specific steps are as follows: 1. Sequence structure optimization of ligand dipeptide The dipeptide sequences were input into Discovery Studio software to obtain the three-dimensional structures of 400 dipeptide sequences. Then, energy optimization was performed using the CHARMM force field to obtain ligand files that can be used for molecular docking. 2. Processing of receptor XOD Download the XOD crystal structures from the PDB database, numbered 1FIQ. Preprocess the structure files by removing water and adding hydrogen to achieve a protonated state. Then define the active sites of the protein and save them in pdbqt format for high-throughput molecular docking screening. 3. Molecular docking prediction The docking procedure was run using the semi-flexible CDOCKER docking mode in molecular docking. Molecular docking results were characterized by CDOCKER energy score, CDOCKER interaction energy score, interaction sites, and interaction force type. Higher spatial fit between the ligand and receptor resulted in a higher system score, indicating a stronger interaction and potentially stronger receptor inhibitory activity. Results are as follows: Figure 1 As shown in B, 400 dipeptides were assigned different scores, and dipeptides with different scores were randomly selected for the next in vitro validation experiment. Specific Implementation Example 2 Establishment of an in vitro xanthine oxidase activity system and evaluation of its inhibitory effect on dipeptides. At room temperature, 20 μL of different dipeptide concentration gradients of 0, 10, 20, 30, 40, 50, and 60 mg / mL were pre-reacted with 20 μL of 0.05 U / mL xanthine oxidase for 3 minutes. Then, 60 μL of 0.4 mmol / L xanthine was added and the reaction was carried out at 37 °C for 25 minutes. Finally, 32 μL of 1 mol / L hydrochloric acid solution was added. The reaction system was filtered through a 0.22 μm filter membrane, and the uric acid content was analyzed by HPLC. The HPLC detection conditions were as follows: Agilent 1200 series high-performance liquid chromatography; ZORBAX OriginalPhenyl column (5μm, 4.6×250mm); mobile phase A was aqueous phase containing 0.52mM sodium 1-pentanesulfonate and 0.20M dipotassium hydrogen phosphate to a final concentration, and the pH of mobile phase A was adjusted to 4.0 with phosphoric acid solution; mobile phase B was chromatographic grade acetonitrile; mobile phase A:mobile phase B = 85:15 (V / V); flow rate was 1.0mL / min; detection wavelength was 290nm; and injection volume was 10μl.

[0015] like Figure 1 As shown in Figure C, at a concentration of 60 mg / mL, the inhibition rates of xanthine oxidase by DK, AG, KE, YI, CE, and KN reached 82.21%, 76.29%, 67.01%, 43.92%, 43.38%, and 33.58%, respectively. At a concentration of 40 mg / mL, the inhibition rates of DK, AG, KE, YI, CE, and KN were 57.86%, 52.86%, 48.95%, 38.53%, 29.90%, and 29.6%, respectively. The inhibition rates of other dipeptides VM, KI, KM, and GP at 40 mg / mL were 24.32%, 13.32%, 9.51%, and 6.04%, respectively. Figure 1As shown in D, Pearson correlation analysis was performed on the software scoring results of different dipeptides and the actual in vitro enzyme activity inhibition rate data. The correlation coefficient R = 0.8684 was found, which proves that the software scoring results and the actual in vitro enzyme activity inhibition rate have a strong positive correlation, indicating that it is feasible to use software scoring to predict the in vitro enzyme activity inhibition rate of dipeptides. Specific Implementation Example 3 I. Experimental Materials Human renal cortical proximal tubular epithelial cells HK-2 were purchased from Wuhan Pronosei Life Science Technology Co., Ltd. CCK-8 reagent (catalog number K1018) was purchased from Apbai Biotechnology Co., Ltd. Gibco premium fetal bovine serum (catalog number 10099), penicillin (catalog number 11593027), and streptomycin (catalog number 11860038) were purchased from Thermo Fisher Scientific. Gibco DMEM / F-12 cell culture medium (catalog number 11330032) was purchased from Thermo Fisher Scientific. DMEM / F-12 cell culture medium is a widely used basal medium for promoting the growth of many different mammalian cells, using a 1:1 mixture of DMEM and Ham's F-12.

[0017] II. Detection of dipeptide cytotoxicity First, the cytotoxicity of the dipeptide on human renal cortical proximal tubular epithelial cells HK-2 was tested. Cells were seeded at 5000 cells / well in 96-well plates, and DMEM / F12 complete medium (DMEM / F12 medium supplemented with 10% fetal bovine serum, 100 μg / mL streptomycin, and 100 units / mL penicillin) was added. The cells were cultured at 37°C and 5% CO2 for 24 hours to allow complete cell adhesion.

[0018] 10 μL of allopurinol at different concentrations (0.1-0.5 mM) was added to the cell culture system to detect the toxicity of allopurinol to cells. After culturing in the same environment for 24 hours, the effect of the treatment on cell viability was verified according to the CCK8 kit procedure. Figure 2 As shown in Figure A, the addition of different concentrations of allopurinol had no significant effect on cell viability, demonstrating that allopurinol is not cytotoxic within the tested concentration range (0.1-0.5 mM).

[0019] 10 μL of different concentrations of dipeptide (0.25-0.10 mM) were added to the cell culture system to detect the toxicity of the dipeptide to cells. After culturing in the same environment for 24 hours, the effect of the treatment on cell viability was verified according to the CCK8 kit procedure. Figure 2As shown in Figure C, the addition of different concentrations of dipeptide had no significant effect on cell viability, demonstrating that all tested dipeptides were non-cytotoxic within the test concentration range (0.25-0.10 mM).

[0020] III. Detection of the uric acid-lowering activity of dipeptides at the cellular level A cell model of hyperuricemia was established using HK-2 cells based on the principle of adenosine induction.

[0021] Cells were arranged in a 1*10 6 Cells were seeded per well in 6-well plates and cultured in DMEM / F12 complete medium (DMEM / F12 medium supplemented with 10% fetal bovine serum, 100 μg / mL streptomycin, and 100 units / mL penicillin) for 48 hours to ensure complete cell adhesion. Cells were then divided into control, model, positive control, and dipeptide treatment groups according to the experimental objectives. The following procedures were performed for each group: Control group: The cells were replaced with fresh DMEM / F12 complete medium and cultured for another 24 h. The cells were washed with PBS buffer to remove any residual complete medium. DMEM / F12 medium (containing 100 μg / mL streptomycin and 100 units / mL penicillin) was added and the cells were cultured for another 30 h. Then, 0.005 U / mg xanthine oxidase was added and the cells were cultured for another 8 h. The supernatant was collected, filtered through a 0.22 μm filter membrane, and the uric acid concentration was quantitatively analyzed by HPLC.

[0022] Model group: The cells were replaced with fresh DMEM / F12 complete medium and cultured for another 24 h. The cells were washed with PBS buffer to remove any residual complete medium. DMEM / F12 medium (containing 100 μg / mL streptomycin and 100 units / mL penicillin) was added, along with a final concentration of 2.5 mmol / L adenosine solution. After culturing for 30 h, 0.005 U / mg xanthine oxidase was added and the cells were cultured for another 8 h. The supernatant was collected, filtered through a 0.22 μm filter membrane, and the uric acid concentration was quantitatively analyzed by HPLC.

[0023] Positive control group (low-dose group): Fresh DMEM / F12 complete medium was added, along with a final concentration of 100 μM allopurinol. The cells were cultured for another 24 h. Cells were washed with PBS buffer to remove any residual complete medium. DMEM / F12 medium (containing 100 μg / mL streptomycin and 100 units / mL penicillin) was added, along with a final concentration of 2.5 mmol / L adenosine solution and 100 μM allopurinol. After culturing for 30 h, 0.005 U / mg xanthine oxidase was added, and the cells were cultured for another 8 h. The supernatant was collected, filtered through a 0.22 μm filter membrane, and the uric acid concentration was quantitatively analyzed by HPLC.

[0024] Positive control group (high-dose group): Fresh DMEM / F12 complete medium was added, along with a final concentration of 500 μM allopurinol. The cells were cultured for another 24 h. Cells were washed with PBS buffer to remove any residual complete medium. DMEM / F12 medium (containing 100 μg / mL streptomycin and 100 units / mL penicillin) was added, along with a final concentration of 2.5 mmol / L adenosine solution and 500 μM allopurinol. After culturing for 30 h, 0.005 U / mg xanthine oxidase was added, and the cells were cultured for another 8 h. The supernatant was collected, filtered through a 0.22 μm filter membrane, and the uric acid concentration was quantitatively analyzed by HPLC.

[0025] Dipeptide treatment group (low-dose group): Fresh DMEM / F12 complete medium was replaced, and a final concentration of 2.5 mM dipeptide was added. The cells were cultured for another 24 h. Cells were washed with PBS buffer to remove residual complete medium. DMEM / F12 medium (containing 100 μg / mL streptomycin and 100 units / mL penicillin) was added, along with a final concentration of 2.5 mmol / L adenosine solution and 2.5 mM dipeptide. After culturing for 30 h, 0.005 U / mg xanthine oxidase was added, and the cells were cultured for another 8 h. The supernatant was collected, filtered through a 0.22 μm filter membrane, and the uric acid concentration was quantitatively analyzed by HPLC.

[0026] Dipeptide treatment group (medium dose group): Fresh DMEM / F12 complete medium was replaced, and a final concentration of 5 mM dipeptide was added. The cells were cultured for another 24 h. Cells were washed with PBS buffer to remove residual complete medium. DMEM / F12 medium (containing 100 μg / mL streptomycin and 100 units / mL penicillin) was added, along with a final concentration of 2.5 mmol / L adenosine solution and 5 mM dipeptide. After culturing for 30 h, 0.005 U / mg xanthine oxidase was added, and the cells were cultured for another 8 h. The supernatant was collected, filtered through a 0.22 μm filter membrane, and the uric acid concentration was quantitatively analyzed by HPLC.

[0027] Dipeptide treatment group (high-dose group): Fresh DMEM / F12 complete medium was added, and a final concentration of 10 mM dipeptide was added. The cells were cultured for another 24 h. Cells were washed with PBS buffer to remove residual complete medium. DMEM / F12 medium (containing 100 μg / mL streptomycin and 100 units / mL penicillin) was added, along with a final concentration of 2.5 mmol / L adenosine solution and 10 mM dipeptide. After culturing for 30 h, 0.005 U / mg xanthine oxidase was added, and the cells were cultured for another 8 h. The supernatant was collected, filtered through a 0.22 μm filter membrane, and the uric acid concentration was quantitatively analyzed by HPLC.

[0028] Figure 2B indicates that when the allopurinol concentrations were 100 and 500 μM, the uric acid concentration in the cell supernatant decreased by 13.64% and 87.95% respectively compared to the model group, indicating that high-dose allopurinol has better uric acid-lowering activity at the cellular level.

[0029] Figure 2 D indicates that as the dipeptide concentration increases, the uric acid content in the cell supernatant gradually decreases, and the uric acid-lowering activity gradually increases. At a concentration of 10 mM, the uric acid content in the cell supernatant of the dipeptide KE, YI, KN, CE, DK, and AG treatment groups decreased by 38.37%, 32.90%, 27.55%, 25.61%, 18.71%, and 5.12% respectively compared to the model group. Among all the dipeptides tested, dipeptides KE, YI, and KN showed the best uric acid-lowering effect at the cellular level.

[0030] IV. Effects of dipeptides on the expression of key genes in cells Given that KE, YI, and KN exhibited better uric acid-lowering activity compared to other tested dipeptides, their gene expression at protein levels was investigated. Total protein was extracted from the control group, model group, and high-dose dipeptide treatment group (10 mM group) using a protein extraction kit, and Western blotting experiments were performed.

[0031] Figure 3 A represents the detection of the expression levels of proteins ADA (adenosine deaminase) and XOD (xanthine oxidase). ADA and XOD are key proteins involved in uric acid synthesis. The results showed that, compared with the control group, the expression level of ADA protein was significantly increased in the model group, while KE, YI, and KN treatments all inhibited ADA protein expression; furthermore, neither the modeling treatment nor the dipeptide treatment had a significant effect on XOD protein expression.

[0032] Figure 3 B represents the detection of the expression levels of proteins ABCG2 (multidrug transporter 2) and GLUT9 (glucose transporter 9). ABCG2 is responsible for uric acid efflux, while GLUT9 is responsible for uric acid reabsorption. The results showed that, compared with the control group, the model group had increased ABCG2 protein expression, while treatment with peptides KE, YI, and KN inhibited ABCG2 protein expression, but there were no significant differences between groups. Simultaneously, compared with the control group, the model group had decreased GLUT9 protein expression, and treatment with peptides KE, YI, and KN further inhibited GLUT9 protein expression, but there were no significant differences between groups. This indicates that adenosine-induced modeling and dipeptide intervention primarily target the uric acid synthesis pathway. Specific Implementation Example 4 The uric acid-lowering effect of dipeptide in mouse models ICR mice were bred by Hauschka using Swiss mice with the goal of high productivity. Later, the Institute of Cancer Research in the United States distributed them to various countries for breeding and experimentation, and they were called ICR mice in those countries.

[0034] ICR mice aged 4-6 weeks were purchased and given a week of free access to food to acclimatize. Subsequently, the mice were randomly divided into a control group, a model group, an allopurinol group, and treatment groups with KE, KN, and YI. The experimental procedures are as follows: Control group: mice were administered physiological saline by gavage for 3 days; starting from day 4, 0.25% sodium carboxymethyl cellulose was injected intraperitoneally 1 hour after the physiological saline gavage, continuing until day 14. On day 14, blood was collected from the eyeballs of mice 30 minutes after the intraperitoneal injection, and the mice were euthanized.

[0035] Model group: mice were administered physiological saline by gavage for 3 days; starting from day 4, 1 hour after gavage with physiological saline, mice were intraperitoneally injected with 250 mg / kg potassium oxonate and 150 mg / kg hypoxanthine (dissolved in 0.25% sodium carboxymethyl cellulose), continuing until day 14. On day 14, 30 minutes after the intraperitoneal injection, blood was collected from the eyeballs of mice and they were euthanized.

[0036] Positive control group: Mice were administered 10 mg / kg allopurinol by gavage for 3 days. Starting on day 4, 1 hour after gavage with 10 mg / kg allopurinol, mice were intraperitoneally injected with 250 mg / kg potassium oxonate and 150 mg / kg hypoxanthine (dissolved in 0.25% sodium carboxymethyl cellulose), continuing until day 14. On day 14, blood was collected from the eyeballs of mice 30 minutes after the intraperitoneal injection, and the mice were euthanized.

[0037] Peptide treatment group: Mice were administered 15 mg / kg dipeptide by gavage for 3 days; starting from day 4, 1 hour after gavage administration of 15 mg / kg dipeptide, mice were intraperitoneally injected with 250 mg / kg potassium oxonate and 150 mg / kg hypoxanthine (dissolved in 0.25% sodium carboxymethyl cellulose), continuing until day 14. On day 14, blood was collected from the eyeballs of mice 30 minutes after intraperitoneal injection, and the mice were euthanized.

[0038] Serum uric acid content was detected by HPLC; serum xanthine oxidase activity was detected by a kit (Nanjing Jiancheng Bioengineering Research Institute Co., Ltd., catalog number A002-1-1).

[0039] Blood uric acid levels such as Figure 4As shown in Figure A, compared with the control group, intraperitoneal injection of potassium oxonate and hypoxanthine increased serum uric acid levels in the model group by 31.5 times, while allopurinol and dipeptide treatment both reduced serum uric acid levels. Compared with the model group, the positive control group showed a 95.0% reduction in serum uric acid levels, which was superior to the three dipeptides tested. Among the dipeptides, KN ​​showed the best uric acid reduction, decreasing uric acid levels by 82.1% compared with the model group; followed by KE, which reduced uric acid levels by 57.0% compared with the model group.

[0040] Serum xanthine oxidase activity such as Figure 4 As shown in B. Compared with the control group, the serum xanthine oxidase activity in the model group increased by 53.2%; compared with the model group, the inhibition rates of serum xanthine oxidase activity in mice in the allopurinol, KE, KN and YI groups were 38.9%, 50.0%, 43.1% and 41.7%, respectively. Specific Implementation Example 5 The dipeptides KE and KN, which have shown high inhibitory activity both in vivo and in vitro, were selected as replacement elements. Using the hexapeptide GPAGPR, which has been reported to have uric acid-lowering activity, as a template, targeted modification of the active peptides was performed. The modified active peptide sequences are KEAKER and KNAKNR. Figure 5 A).

[0042] At a peptide concentration of 40 mg / ml, the in vitro xanthine oxidase inhibition rate of the urate-lowering peptide template GPAGPR was 37.3%, the inhibition rate of the dipeptide element GP was 6.0%, and the inhibition rate of the dipeptide element KN was 29.6%. After replacing GP with KN in the template, the active peptide KNAKNR showed an inhibition rate of 48.3%; the inhibition rate of the dipeptide element KE was 49.0%, and after replacing GP with KE in the template, the active peptide KEAKER showed an inhibition rate of 66.4%. Figure 5 B).

[0043] The foregoing description is not intended to limit the invention, nor is the invention limited to the examples given. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the invention should also be considered within the protection scope of the invention.

Claims

1. The application of a xanthine oxidase inhibitory peptide in the preparation of uric acid-lowering drugs or adjuvant drugs for the treatment of gout, characterized in that... The amino acid sequence of the inhibitory peptide is: KEAKER and / or KNAKNR.

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