Tryptophan residue enhances in vitro walnut protein-derived peptides exerting xanthine oxidase inhibition and antioxidant activities

The modulation of xanthine oxidase (XO) activity is critical to the treatment of hyperuricemia and oxidative stress-related disease. Although the walnut protein hydrolysates had been reported to inhibit XO, their interaction mechanism remained unclear. Herein, the walnut protein-derived peptides were used to evaluate their in vitro XO-inhibitory activity and their inhibitory mechanism. The results suggested that Trp-containing walnut protein-derived peptides were able to effectively inhibit XO, moreover, the increased number of Trp would significantly enhance the XO-inhibitory activity of Trp-containing peptides. Similar to the allopurinol, Trp had active interaction with the critical residues Glu802, Leu873, Ser876, Arg880, Phe914, Phe1009, Thr1010, Val1011, Leu1014, Ala1078, Ala1079 and molybdopterin MOS3004 of XO, making Trp-containing peptide have high XOI activity. Simultaneously, the Trp-containing walnut protein-derived peptide also had been found to show great potential in antioxidant activity. Present work would introduce functional food-derived peptides for the improvement of hyperuricemia and oxidative stress-related disease.