Technology optimization on preparation of XOD inhibition peptide from Saury

Abstract: During the metabolism in human body, the purines from food, nucleic acid and adenosine triphosphate (ATP) would all turn into hypoxanthine, and then the hypoxanthine would change into uric acid treated by xanthine oxidase (XOD). Thus the XOD plays a key role during the whole process. In addition, it has been reported that the XOD can not only combine with hypoxanthine, but also do with pyrazolopyrimidines, purines, phenylprazole derivatives, flavones and so on. Therefore, uric acid can be decreased by combining heterocyclic compounds with XOD. Recently, the western medicines have been widely used in the treatment of the high uric acid and gout, but some side effects from these western medicines may appear on human body. Allopurinol is the only drug in the medicine market which reduces the production of uric acid through the inhibition of XOD, but it is also proved to have side effects on liver and kidney. With the development of the enzymatic hydrolysis technology, more and more bioactive peptides have been prepared and studied for drug use or health care. The small peptides have many advantages, for example, they are safe without any side effects and can be absorbed more quickly. The saury is mostly used to only produce can and dry foods due to the backward science and technology, which doesn't fully tap its potential economic and nutritional value. In fact, the saury is very rich in protein and it might have many special functions due to the hard environment in the sea. Therefore, the saury might be a perfect raw protein material for the preparation of the urate-lowering peptide. This can bring not only better nutrition but also higher economic value. In the present paper, the XOD inhibition peptide was prepared by hydrolyzing saury. By detecting the protein recovery and inhibition activity of XOD of different hydrolysates, the neutral protease and pancreatin were proved the best protease through the single factor experiment. Then the effects of protease concentration, hydrolysis time and ratio of neutral protease on protein recovery and inhibition activity of XOD were studied by using response surface method to improve the preparing technology. Results showed that protease concentration and ratio of neutral protease had a significant influence on the protein recovery (P<0.001), while protease concentration and hydrolysis time had a significant effect on inhibition activity of XOD (P<0.001). The best technology of preparing the XOD inhibition peptides from saury was optimized based on the research results above. The best process parameters were as follows: the ratio of liquor to material was set to 1:2, the total protease concentration was 0.3% (the pancreatin accounted for 40% and the neutral protease accounted for 60%), the pH value of the enzymatic hydrolysis system was 7.0, the temperature was 55℃, and the hydrolysis time was 6 h. The theoretical protein recovery rate could reach 72.69%, and the theoretical inhibition activity of the XOD was 30.32%. The established model was of high reliability, and it could be used to prepare the XOD inhibition peptide from saury hydrolysate. The test of molecular weight distribution indicated that saury hydrolysate mainly consisted of the peptide fragments smaller than 3 kDa (76.35%). The paper indicated that the saury hydrolysate with XOD inhibition peptide was a potential material for decreasing uric acid in food industry.