Identification of novel dipeptidyl peptidase-4 inhibitory peptides from pea proteins: A combined in silico and in vitro study

Dipeptidyl Peptidase 4 inhibitory peptides (DPP-4IPs) could exhibit their hypoglycemic effects by preventing Glucagon-like peptide 1 (GLP-1) degradation. However, identifying DPP-4IPs by traditional approach is laborious. Therefore, this study aims to rapidly identify DPP-4IPs by an in silico method. After in silico digestion, 509 peptide fragments were obtained from pea proteins. Subsequently, two novel DPP-4IPs SPGDVF and EPF with the in vitro half-maximal inhibitory concentrations (IC50) values of 277.61 and 406.47 mu M were obtained by virtual screening and molecular docking. Interestingly, their in situ DPP-4 IC50 values in Caco-2 cells were increased to 918.82 and 1868.27 mu M, respectively. Lineweaver-Burk double-reciprocal plots revealed that SPGDVF and EPF were competitive and mixed-type DPP-4IPs, respectively. Significantly, molecular docking suggested that SPGDVF could bond with DPP-4 active pockets. While EPF only bound outside of these active pockets, which may be the reason that EPF was weaker than SPGDVF in DPP-4 inhibition. Overall, this work provides a convenient strategy for identifying DPP-4IPs from food proteins.