Investigation of the Potential of Hemp, Pea, Rice and Soy Protein Hydrolysates as a Source of Dipeptidyl Peptidase IV (DPP-IV) Inhibitory Peptides

Food protein hydrolysates contain peptide sequences with dipeptidyl peptidase IV (DPP-IV) inhibitory properties which may find use to improve serum glucose regulation in type 2 diabetics. Four plant protein isolates from hemp (H), pea (P), rice (R) and soy (S) were hydrolysed with three enzyme preparations: Corolase L10 (Cor), Promod 144MG (Prom) and Protamex (Prot). From the 12 hydrolysates generated after 4-h incubation, 7 yielded DPP-IV inhibitory activity <2.0 mg protein equivalent mL⁻¹. Their IC₅₀ values ranged from 0.73 ± 0.11 to 3.54 ± 0.24 mg dry weight (dw) hydrolysate mL⁻¹ for the 4 h P_Prot and 4 h H_Cor hydrolysates, respectively. Simulated gastrointestinal digestion (SGID) of the intact proteins yielded DPP-IV IC₅₀ values between 1.85 ± 0.34 and 4.50 ± 0.55 mg dw hydrolysate mL⁻¹ for the R and H, respectively. The DPP-IV inhibitory potency of the 4 h hydrolysates subjected to SGID (DPP-IV IC₅₀ ranging from 1.00 ± 0.42 to 3.83 ± 0.36 mg dw hydrolysate mL⁻¹ for the SGID of the 4 h S_Prom and 4 h H_Prot, respectively) was generally higher than that of the corresponding intact protein subjected to SGID, with the exception of the SGID of R and that of the 4 h R_Prot hydrolysate which had similar IC₅₀ values (P > 0.05). To our knowledge, this is the first study reporting that H and P protein hydrolysates inhibit DPP-IV in vitro. This study also demonstrates the potential benefit, in some instances, of hydrolysing plant protein substrates prior to oral ingestion with the view of releasing DPP-IV inhibitory peptides.