Presence of Exopeptidase-Resistant and Susceptible Peptides in a Bacterial Protease Digest of Corn Gluten.

Corn gluten hydrolysate (CGH) was prepared by food-grade bacterial proteases, alcalase and neutral protease. Digestion of CGH with carboxypeptidase A and leucine aminopeptidase extensively changed the elution patterns of peptides as observed from reversed phase high performance liquid chromatography-mass spectrometry (LC-MS), whereas digestion with pepsin and trypsin hardly affected the elution patterns. Twenty-five major peptides in CGH were identified. After digestion with exopeptidases, only prolyl dipeptides and pyroglutamyl di- and tripeptides remained, whereas the other 17 peptides completely disappeared. On the other hand, all 25 peptides remained after digestion with pepsin and trypsin. These facts suggest that a majority of short-chain peptides in food protein hydrolysates are degraded by exopeptidases during digestion and absorption processes. Thus, susceptibility to exopeptidases should be considered for prediction of bioactive peptide upon ingestion, which has not been considered in most of previous studies on food-derived bioactive peptides.