title: Characteristics of activation of cathepsin B by sodium salicylate and comparison of catalytic site properties of cathepsins B and H.
abstract: Attempts to gain greater understanding of characteristics of catalytic site properties of two homologous lysosomal cysteine proteinases, cathepsins B and H, were made by using sodium salicylate (SA) and several specific inhibitors, which extends the studies on the structure-activity relationship and kinetics for the activation of cathepsin B by SA in the previous paper (Yamamoto, K., Takeda, M. and Kato, Y.: Japan. J. Pharmacol. 38, 215-218, 1985). The half-maximal activation of cathepsin B by SA was observed at around a molar ratio of 10(4):1 (SA/cathepsin B). No preincubation time was needed for the SA-stimulated reaction, but the rate of activation was more rapid as pH values in the preincubation mixture decreased. The extent of inactivation of cathepsin B by leupeptin and E-64 significantly decreased in the presence of SA. Catalytic site properties of cathepsins B and H were also distinguished by differences in the extent of inhibition by cysteine proteinase inhibitors. Cathepsin B was more sensitive than cathepsin H to inhibition by antipain, chymostatin, iodoacetic acid and mercuric chloride as well as leupeptin and E-64. Despite the similarity in inhibitory effects of iodoacetic acid and E-64, the rat spleen cathepsin H was characterized by insensitivity to mercuric chloride that had a considerable inhibitory effect on the corresponding enzyme from rat liver and the rat spleen cathepsin B.
mesh_terms: D000818:Animals; D002384:Catalysis; D002401:Cathepsin B; D056655:Cathepsin H; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002848:Chromatography, DEAE-Cellulose; D003545:Cysteine / Q000494:pharmacology; D003546:Cysteine Endopeptidases; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D051381:Rats; D012459:Salicylates / Q000494:pharmacology*; D020156:Salicylic Acid; D013154:Spleen / Q000201:enzymology
chemical_list: D012459:Salicylates; D002403:Cathepsins; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056655:Cathepsin H; C534128:Ctsh protein, rat; D003545:Cysteine; D020156:Salicylic Acid