Inhibition properties of dipeptides from salmon muscle hydrolysate on angiotensin I-converting enzyme


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We isolated Phe–Leu as an angiotensin I-converting enzyme (ACE) inhibitor from hydrolysate of chum salmon muscle. The IC50 value of this peptide was 13.6 μm, and it showed non-competitive inhibition. The reverse sequence dipeptide Leu–Phe also showed ACE inhibitory activity. However, Leu–Phe is much less inhibitory than Phe–Leu with an IC50 value of 383.2 μm. In addition, the inhibition mode was competitive. To investigate the relationship between dipeptide sequence and ACE inhibition properties, we further measured ACE inhibitory activity and inhibition mechanism using six Trp-containing dipeptides, which had been identified from the same salmon muscle hydrolysate as ACE inhibitory peptides in a previous study. Peptides with Trp as the C-terminal residue, Ala–Trp, Val–Trp, Met–Trp, Ile–Trp, Leu–Trp showed non-competitive inhibition. On the other hand, reversed sequence peptides with Trp at the N-terminal were competitive inhibitors, except Trp–Leu. These results indicate that the sequence of ACE inhibitory dipeptides can affect both inhibitory potency and the inhibition mechanisms.