Generation of wheat gluten hydrolysates with dipeptidyl peptidase IV (DPP-IV) inhibitory properties

Wheat gluten, a Pro-rich dietary protein, was investigated for its potential to produce dipeptidyl peptidase IV (DPP-IV) inhibitory peptides during enzymatic hydrolysis with Debitrase HYW20. Nine gluten hydrolysates (H1-H9) were generated using a 2 factor × 3 level design of experiments (DOE) including the incubation temperature (40, 50 and 60 °C) and the enzyme: substrate ratio (E : S, 0.5, 1.0 and 1.5% (w/w)). Their DPP-IV half maximal inhibitory concentration (IC₅₀) ranged from 0.24 ± 0.02 (H9) to 0.66 ± 0.06 mg mL^-1 (H2A and H7) and their degree of hydrolysis (DH) from 31.7 ± 0.9 (H7) to 62.2 ± 3.0% (H6). Gluten and H9, the most potent DPP-IV inhibitory hydrolysate, were subjected to simulated gastrointestinal digestion (SGID), yielding Gluten-CorPP and H9-CorPP, respectively. H9-CorPP had a higher DPP-IV inhibitory potency than Gluten-CorPP (i.e., DPP-IV IC₅₀ values of 0.33 ± 0.03 vs. 1.45 ± 0.26 mg mL^-1, respectively). H9 and H9-CorPP both contained relatively potent DPP-IV inhibitory peptides such as Val-Pro-Leu, Trp-Leu and Trp-Pro which were identified by liquid chromatography tandem mass spectrometry (LC-MS/MS). In addition, several sequences possessing features of DPP-IV inhibitory peptides, mostly consisting of a penultimate or C-terminal Pro, were identified within H9. The presence of Pro-containing peptides within H9 may contribute to its stability to digestive enzymes. Gluten hydrolysates may have antidiabetic potential for humans.