Angiotensin I converting enzyme inhibitory peptides generated from oligopeptides by intestinal mucosa peptidases

Peptide hydrolases were prepared from porcine small intestinal mucosa and their properties were examined using the following peptide substrates : Arg-Lys-Glu-Val-Tyr, Arg-Lys-Asp-Val-Tyr, Val-Tyr-Val, ACE inhibitory dipeptides, and other dipeptides. Peptide hydrolases hydrolyzed all the peptides above cited, and released the amino acid from the NH₂-terminus of the tri and pentapeptides. Ile-His, Gly-Pro, Phe-Pro, His-Pro, Pro-Phe, Asp-Glu, Asp-Asp, Glu-Glu, Glu-Asp, Gly-Sar, Pro-Gly, and Val-Tyr showed resistance to dipeptidases, but, Gly-Trp, Met-Phe, and Arg-Tyr, with ACE inhibitory activity were rapidly hydrolyzed. Glu-Val-Tyr and Asp-Val-Tyr rapidly released Glu and Asp, respectively, as tri and aminopeptidases. The results suggested that the primary structure of dipeptides, tripeptides, and oligopeptides are involved in ACE activity. Val-Tyr is a major ACE inhibitory peptide derived from sardines. Also, oligopeptides having Val-Tyr at the COOH-terminus were rapidly hydrolyzed by peptide hydrolases including tri and aminopeptidases from porcine small intestinal mucosa, but, resistant Val-Tyr had a potent ACE inhibitory activity.