title: Inhibition of human converting enzyme in vitro by a novel tripeptide analog.
abstract: We have studied inhibition of homogeneous human converting enzyme by a new inhibitor, a ketomethylene derivative of the blocked tripeptide substrate, Bz-Phe-Gly-Pro (ketoACE). KetoACE inhibited the hydrolysis of Hip-His-Leu and Hip-Phe-Arg at different concentrations (I50 values were 4 X 10(-8) M and 2 X 10(-7) M, respectively). Kinetic studies indicated that ketoACE inhibits the hydrolysis of both substrates by a similar, non-competitive mechanism. At the lowest enzyme concentration tested, using 3H-Hip-Gly-Gly as substrate, the I50 of ketoACE was 6 X 10(-9) M. KetoACE protected a functional tyrosine residue in the active site of human converting enzyme from modification with N-acetylimidazole. It is proposed that there are alternate (hydrophobic) binding sites for both inhibitors and substrates in the active site of human converting enzyme. It should be possible to develop other high-affinity inhibitors of this class that bind to hydrophobic sites and do not require metal binding via a sulfhydryl group.
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors; D001665:Binding Sites; D006801:Humans; D007700:Kinetics; D009842:Oligopeptides / Q000494:pharmacology*; D011392:Proline / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D009842:Oligopeptides; D011392:Proline