Exploring structural features of potent dipeptidyl peptidase IV (DPP-IV) inhibitory peptides derived from tilapia (Oreochromis niloticus) skin gelatin by an integrated approach of multivariate analysis and Gly-Pro-based peptide library

There are abundant dipeptidyl-peptidase IV (DPP-IV) inhibitory peptide motifs in collagen sequences due to high content of Pro. However, the structural features of the most potent DPP-IV inhibitory peptides were not fully elucidated. In this study, peptides from tilapia skin gelatin hydrolysates with different DPP-IV inhibitory activities were analyzed by UPLC-MS/MS and multivariate analysis, and a Gly-Pro-type peptide library was constructed to elucidate their structural features. Results showed that peptide length had a dominant effect on the DPP-IV inhibition of collagen-derived peptides. Moreover, Gly-Pro-type peptides (e.g., GPA- and GPI- types) containing 4 similar to 9 residues showed a potent DPP-IV inhibition, the IC50 values of which were 2.15 similar to 10.43 times lower than that of Gly-Pro-Xaa tripeptides. More importantly, different proteases had discrepancy in releasing these peptides, among which papain could release them to a greater extent due to its strong preference for Arg in the S1 subsite and Pro in the S3 subsite.