Angiotensin converting enzyme-inhibitory activity of peptides isolated from Manchego cheese. Stability under simulated gastrointestinal digestion

In this study, several peptides, which had previously been identified in active HPLC fractions from Manchego cheese, were synthesised and their angiotensin converting enzyme (ACE)-inhibitory activities were measured. From 11 peptides, which were selected based on their structures, only two, VRYL and KKYNVPQL, showed considerable ACE-inhibitory activity with IC50 values of 24.1 and 77.1 mum, respectively. Subsequently, the impact of the gastrointestinal digestion on ACE-inhibitory activity was evaluated. Some of the peptides selected were resistant to the incubation with pepsin followed by hydrolysis with a pancreatic extract. The ACE-inhibitory activity after simulated digestion did not change drastically except for peptide alpha(sc)-CN f(195-204) (TQPKTNAIPY) that exhibited an activity 6 times greater after simulated digestion. In contrast, after simulated digestion, the activities of peptides VRYL and KKYNVPQL decreased. The peptides not hydrolysed by gastrointestinal enzymes and peptide VRYL, which was only partly hydrolysed, were incubated with ACE and were found to be true inhibitors of the enzyme and to have a competitive inhibition pattern. (C) 2004 Elsevier Ltd. All rights reserved.