Isolation of Acein-2, a novel angiotensin-I-converting enzyme inhibitory peptide derived from a tryptic hydrolysate of human plasma

We previously described a novel angiotensin-I-converting enzyme (ACE) inhib itory peptide, designated Acein-1, that Nas isolated from a tryptic hydroly sate of human plasma. We now report a second such inhibitory peptide, Acein -2 obtained from the same hydrolysate. The peptide was purified by gel filt ration and cation exchange chromatography followed by reversed-phase gradie nt and isocratic high performance Liquid chromatography. Acein-2 mas found to be a tripeptide, Leu-Ile-Tyr, which is thought to correspond to f(518-52 0) of human alpha 2-macroglobulin, The synthetic tripeptide showed a potent dose-dependent inhibition of ACE, with an IC50 value of 0.82 mu mol/l. Lin eweaver-Burk plots suggested that Acein-2 as well as the previously describ ed Acein-1 are non-competitive inhibitors. (C) 2000 Federation of European Biochemical Societies.