Identification, inhibitory mechanism and transepithelial transport of xanthine oxidase inhibitory peptides from whey protein after simulated gastrointestinal digestion and intestinal absorption

• XO inhibitory peptides were released from whey protein after GI digestion and intestinal absorption. • Trp-rich short peptide showed the higher XO inhibitory activity. • PEW and LLW interacted with the residues in the active XO cavity and changed the structure of XO. • PEW and LLW transported across Caco-2 monolayers intact through paracellular route and PepT1. • Tight junction proteins ZO-1 and occludin were not destroyed by the peptides. In the present study, xanthine oxidase (XO) inhibitory peptides were identified from peptides that survived in whey protein isolate (WPI) simulated gastrointestinal digestion and passed through the Caco-2 cell monolayer, and their inhibitory mechanism and transepithelial transport were investigated. After in silico screening and activity validation, PEW and LLW showed the highest XO inhibitory activity with 50% inhibitory concentrations (IC 50 ) of 3.46 ± 0.22 and 3.02 ± 0.17 mM, respectively. Molecular docking, molecular dynamics simulation, and circular dichroism (CD) results revealed that these two peptides could interact with the residues in the XO active cavity via hydrogen bonds and hydrophobic forces to form a more stable protein-ligand complex, thus affecting the binding of the substrate to XO. Furthermore, PEW and LLW were transported across Caco-2 cell monolayers intact through the paracellular route and peptide transporter 1 (PepT1), and tight junction proteins zonula occludens 1 (ZO-1) and occludin were not disrupted by PEW and LLW. This study suggests that PEW and LLW potentially regulate XO activity in vivo to exert antihyperuricemia effects.