Novel hemoglobin-derived xanthine oxidase inhibitory peptides: Enzymatic preparation and inhibition mechanisms

Xanthine oxidase (XO) activity is critical to modulate uric acid and hyperuricemia. Hemoglobin was hydrolyzed by bromelain and the protease from Geobacillus stearothermophilus (GsProS8) to express excellent protein re-covery rate (54.87%) and XO inhibitory activity (IC50 of 0.744 mg/mL), resulting from higher contents of tryptophan, glutamic acid and glycine. The hydrolysate was fractionated and identified three novel XO inhibitory peptides IVYPW, YPWTQ, and LITGLW (IC50 of 0.63-1.09 mM). Unlike allopurinol, IVYPW and YPWTQ were mixed-type inhibitors, whereas LITGLW was a non-competitive inhibitor. In addition to the well-recognized contribution of tryptophan, molecular docking studies revealed tyrosine residue in IVYPW and YPWTQ impor-tantly enhanced XO inhibitory activities via hydrogen-bond and Pi-Sigma interactions with Thr1010 and His875, respectively. The total number of Pi-related interactions positively determined XO inhibition as comparing IVYPW, YPWTQ and LITGLW. This study provided a promising strategy to prepare anti-hyperuricemic peptides and understand inhibition mechanisms for the management of hyperuricemia.

Automated summary

This study demonstrated the potential of hydrolysates from bromelain and Geobacillus stearothermophilus protease (GsProS8) in inhibiting xanthine oxidase (XO) activity. The hydrolysates contained high levels of tryptophan, glutamic acid, and glycine, leading to excellent XO inhibitory activity. Three novel XO inhibitory peptides, IVYPW, YPWTQ, and LITGLW, were identified and characterized. Molecular docking studies revealed important interactions between tyrosine residues in IVYPW and YPWTQ and key amino acids in XO, enhancing the inhibitory activity. This research provides a promising strategy for developing anti-hyperuricemic peptides and understanding the inhibition mechanisms for managing hyperuricemia.