title: The kinetic mechanism of inhibition of human leukocyte elastase by MR889, a new cyclic thiolic compound.
abstract: The cyclic thiolic compound 2-[3-thiophencarboxythio]-N-[dihydro-2(3H)-thiophenone-3-il] - propionamide (MR889) was investigated as inhibitor of endopeptidases. The activity of bovine pancreatic alpha-chymotrypsin, human leukocyte cathepsin G and rabbit liver cathepsin B was not affected by MR889, whereas porcine pancreatic elastase and human leukocyte elastase were inhibited. The kinetic mechanism of inhibition of human leukocyte elastase was of the reversible, slow-binding, fully competitive type. The rate constants for complex formation between MR889 and leukocyte elastase, determined by pre-steady-state kinetic analysis in the presence of a tetrapeptide substrate at 37 degrees and pH 7.40, were kon = 2363 +/- 15 M-1 sec-1, koff = 3.01 +/- 0.34 x 10(-3) sec-1. The inhibition equilibrium constant was Ki = koff/kon = 1.27 +/- 0.15 microM. Ki, calculated from steady-state kinetic experiments, was 1.38 microM. MR889 also inhibited the elastolytic activity of leukocyte elastase, as determined with insoluble elastin as the substrate.
authors.affiliation: Department of Rheumatology, University Hospital, Zurich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Baici
authors.forename: R
authors.initials: R
authors.lastname: Pelloso
authors.forename: D
authors.initials: D
authors.lastname: Hörler
mesh_terms: D002401:Cathepsin B / Q000037:antagonists & inhibitors; D056649:Cathepsin G; D002403:Cathepsins / Q000037:antagonists & inhibitors; D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D019272:Leukocyte Elastase; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors*; D011480:Protease Inhibitors / Q000494:pharmacology*; D012697:Serine Endopeptidases; D013379:Substrate Specificity; D013876:Thiophenes / Q000494:pharmacology*
chemical_list: D011480:Protease Inhibitors; D013876:Thiophenes; C062051:midesteine; D002403:Cathepsins; D012697:Serine Endopeptidases; D002918:Chymotrypsin; C534094:CTSG protein, human; D056649:Cathepsin G; D010196:Pancreatic Elastase; D019272:Leukocyte Elastase; D002401:Cathepsin B