Isolation and identification of dipeptidyl peptidase-IV inhibitory peptides from Sacha inchi meal

BACKGROUNDSacha inchi meal (SIM) is a by-product of oil processing. Our previous studies showed that SIM hydrolysates exhibited dipeptidyl peptidase-IV (DPP-IV) inhibition activity. The objective of the present work was to identify and characterize the bioactive peptides from protein hydrolysates of SIM; enzyme kinetics and peptide-enzyme interaction were also investigated. RESULTSFrom SIM hydrolysates, ten peptides responsible for the activity were identified: GPSRGF (GF-6), FPILSPDPA (FA-9), APYRRGGKI (AI-9), WPYH (WH-4), DPATWLALPT (DT-10), NPEDEFRQQ (NQ-9), APESKPVGV (AV-9), LEWRDR (LR-6), APVYWVQ (AQ-7) and LLMWPY (LY-6). The IC50 values of five peptides (GF-6, WH-4, AQ-7, AV-9 and LY-6) with better inhibitory activity on DPP-IV were within the range of 23.43-128.40 mu mol L-1. AQ-7 had the best activity, with an IC50 value of 23.43 mu mol L-1. Enzyme kinetics indicated the presence of various inhibition types (mixed, non-competitive and competitive). Isothermal titration microcalorimetry showed that the main forces of the binding sites between peptide (GF-6 or AQ-7) and DPP-IV were hydrogen bond, hydrophobic interaction and van der Waals force. The key residues involved in peptide-enzyme interaction were determined by molecular docking. Furthermore, at a concentration of 800 mu mol L-1, GF-6 was found to significantly increase the glucose consumption in insulin-resistant HepG2 cells (P < 0.05) compared with the model group. CONCLUSIONSacha inchi meal-derived peptides displayed potent DPP-IV inhibition activity and could be used in the health food industry and as lead compounds for diabetes therapy. (c) 2023 Society of Chemical Industry.