Structure activity relationship modelling of milk protein-derived peptides with dipeptidyl peptidase IV (DPP-IV) inhibitory activity

Quantitative structure activity type models were developed in an attempt to predict the key featuresof peptide sequences having dipeptidyl peptidase IV (DPP-IV) inhibitory activity. The models were thenemployed to help predict the potential of peptides, which are currently reported in the literature to bepresent in the intestinal tract of humans following milk/dairy product ingestion, to act as inhibitors ofDPP-IV. Two models (z- and v-scale) for short (2–5 amino acid residues) bovine milk peptides, behavingas competitive inhibitors of DPP-IV, were developed. The z- and the v-scale models (p < 0.05, R2of 0.829and 0.815, respectively) were then applied to 56 milk protein-derived peptides previously reported inthe literature to be found in the intestinal tract of humans which possessed a structural feature of DPP-IV inhibitory peptides (P at the N2position). Ten of these peptides were synthetized and tested fortheir in vitro DPP-IV inhibitory properties. There was no agreement between the predicted and experi-mentally determined DPP-IV half maximal inhibitory concentrations (IC50) for the competitive peptideinhibitors. However, the ranking for DPP-IV inhibitory potency of the competitive peptide inhibitorswas conserved. Furthermore, potent in vitro DPP-IV inhibitory activity was observed with two peptides,LPVPQ (IC50= 43.8 ± 8.8 M) and IPM (IC50= 69.5 ± 8.7 M). Peptides present within the gastrointestinaltract of human may have promise for the development of natural DPP-IV inhibitors for the managementof serum glucose.