alpha-chymotrypsin and midesteine

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.

Topics: Cathepsin B; Cathepsin G; Cathepsins; Chymotrypsin; Humans; In Vitro Techniques; Kinetics; Leukocyte Elastase; Pancreatic Elastase; Protease Inhibitors; Serine Endopeptidases; Substrate Specificity; Thiophenes

We investigated the proteinase inhibitory activity of MR 889, a thiolactic acid derivative. It is able to in vitro inhibit at low concentration (10(-5),10(-6)M) the activity of porcine pancreatic elastase, human neutrophil elastase and bovine chymotrypsin. In addition, MR 889 is able to inhibit the residual activity of alpha 2-macroglobulin-trapped human neutrophil elastase, paralleling the efficacy of phenylmethylsufonylfluoride. Finally, MR 889 has been shown to in vitro reduce the burden of elastase- and chymotrypsin-like activity found in sputum sol-phases of patients admitted for chronic bronchitis exacerbation.

Topics: Chymotrypsin; Humans; Kinetics; Pancreatic Elastase; Protease Inhibitors; Sputum; Thiophenes