Isolation and identification of antioxidant and DPP-IV inhibitory peptide PYPYEPYEPYPY from yak bone hydrolysate

A novel peptide PYPYEPYEPYPY from Yak bone hydrolysate (YBG) was purified by Sephadex G-25, RP-HPLC and identified by ESI-TOF-MS. The peptide exhibited some antioxidant activity in HepG2 cells and the dipeptidyl peptidase IV (DPP-IV) inhibition activities in vivo. In HepG2 cells, when the concentration of peptide was 20–160 µM, it could increase the half-lethal rate (LD50) of cells and showed cytoprotective effect, while at 20–40 µM reduced the reactive oxygen species (ROS) content. The peptide PYPYEPYEPYPY exhibited the highest DPP-IV inhibition activities with IC50 value of 189.4 µM among the nine peptides from YBG. Molecular docking predicted the interaction of peptide PYPYEPYEPYPY with DPP-IV residues TRP62, THR304 and SER462, and the binding between them mainly depends on van der Waals forces and hydrogen bonds. Glucose tolerance tests were performed on C57 mice orally administered synthesized PYPYEPYEPYPY. The maximal decrement in the blood glucose was 10.28 ± 0.47 mmol/L induced by one-time gavage of PYPYEPYEPYPY at 100 mg/kg. This is the first report that both DPP-IV inhibitory activity and antioxidant activity have been identified from yak bone hydrolysate.