Collagen peptides with DPP-IV inhibitory activity from sheep skin and their stability to in vitro gastrointestinal digestion

Abstract Collagen is a potential precursor protein for Dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides because of its high content of Pro. Collagen peptides with DPP-IV inhibitory activity were prepared and identified from sheep skin. The peptide sequences with the highest potential for DPP-IV inhibition were recognized by nano LS-MS/MS and in silico analysis. DPP-IV inhibitory activity of collagen peptides usually decreased after digestion, therefore the effect of peptides digestion on DPP-IV inhibitory activity were studied. Four DPP-IV inhibitory peptides resistant to digestive enzymes or having the possibility of generating new DPP-IV inhibitory peptides after digestion were synthesized. The activity of synthetic peptides before and after digestion were also studied. GPAGPIGPV was resistant to digestion and GPAGPOGFPG discharged DPP-IV inhibitory peptides in silico digestion, suggesting that they can maintain high DPP-IV inhibitory activity after digestion. Binding sites of the peptides with DPP-IV were studied by molecular docking, indicating the mechanism of the peptide having DPP-IV inhibitory activity. The results indicated that DPP-IV-inhibitory peptides identified from sheep skin collagen may be functional components in diabetic diet.