title: Mechanistic studies on the inhibition of stromelysin by a peptide phosphonamidate.
abstract: We have investigated the inhibition of the human matrix metalloproteinase stromelysin (SLN) by the peptide phosphonamidate, phthaloyl-N-(CH2)4-P(O2-)-Ile-(beta-naphthyl)Ala-NH-CH3, and find that it is a potent, slow-binding inhibitor of SLN with kon = 2.7 x 10(4) M-1 sec-1, koff = 1.9 x 10(-4) sec-1, and Ki = 7 nM (pH 5.0, 25 degrees C). To probe the mechanism of inhibition, we determined pH-dependencies and solvent deuterium isotope effects. pH-dependencies of the kinetic parameters for inhibition are complex but reflect greater inhibitory potency at lower pH and suggest a mechanism for inhibition that involves the same active site groups as are involved in catalysis. The solvent isotope on kon (kon, H2O/Kon,D2O) is normal and equals 1.5 +/- 0.1. Together with the pH-dependence of inhibition, this value suggests that kon is rate-limited by a process that involves general-acid/general-base catalysis. We propose that kon is rate-limited by general-acid catalyzed ligand exchange of inhibitor for the zinc-bound water molecule.
authors.affiliation: Department of Enzymology, Merck & Co., Rahway, NJ 07065.
authors.forename: M
authors.initials: M
authors.lastname: Izquierdo-Martin
authors.forename: R L
authors.initials: RL
authors.lastname: Stein
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003903:Deuterium; D004151:Dipeptides / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019278:Matrix Metalloproteinase 3; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors*; D008969:Molecular Sequence Data; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D011869:Radioligand Assay; D011994:Recombinant Proteins
chemical_list: D004151:Dipeptides; D009943:Organophosphorus Compounds; D010455:Peptides; D011994:Recombinant Proteins; C089334:N-(((phthalimidyl)butyl)phospho)isoleucyl-beta-naphthylalanine methylamide; D003903:Deuterium; D008666:Metalloendopeptidases; D019278:Matrix Metalloproteinase 3