Peptidomic analysis of the angiotensin-converting-enzyme inhibitory peptides in milk fermented with Lactobacillus delbrueckii QS306 after ultrahigh pressure treatment.

In this study, we assessed the effect of ultrahigh pressure (UHP) treatment on the concentration of peptides and angiotensin-converting enzyme (ACE) inhibitory activity in milk fermented with Lactobacillus delbrueckii QS306. The peptides were identified using peptidomic analysis, and 313 unique peptides were identified. These peptides were derived from 53 precursor proteins. Before and after UHP treatment, 361 (22.2%) peptide sequences exhibited difference, and 53 peptide segments were significantly different. Among them, small peptides (amino acid residues ≤6) isoelectric were point at pH 5-6, and the net charge was mainly positive or neutral. With hydrophobicity and ACE inhibitory activity as screening indicators, 214 small peptides with potential ACE inhibitory activity were identified, and 130 new peptides had potential ACE inhibitory activity. A novel ACE inhibitory peptide VAPFP was synthesized, whose in vitro inhibition rate was 10.56 μmol\/L. Therefore, using peptidomics, the changes in peptide sequences and enhancement in ACE inhibitory activity before and after UHP treatment could be effectively identified in milk fermented with Lactobacillus delbrueckii QS306. This study provided a convenient method for the discovery and identification of new ACE inhibitory peptides.