title: Isolation and characterization of cathepsin B from rabbit testis.
abstract: Cathepsin B (EC 3.4.22.1) has been purified from rabbit testes to apparent homogeneity by chromatography on DE-52, affinity chromatography on organomercurial agarose and subsequent gel filtrations on Sephadex G-75. The enzyme is composed of a single polypeptide of Mr 23,000. Thiol blocking agents and leupeptin abolished the activity of the enzyme completely. The enzyme showed maximum activity at pH 6.0 and 43 degrees C, required 2 mM-cysteine for the optimal activity and had a Km1.45 X 10(-3) M using Z-Arg-beta-naphthylamide as the substrate. However, Z-Arg-Arg-beta-naphthylamide was 12 times more sensitive as a substrate than was Z-Arg-beta-naphthylamide. Rabbit testicular cathepsin B hydrolysed intact proteins. An endogenous inhibitor isolated from the rabbit testes inhibited purified Cathepsin B.
mesh_terms: D000818:Animals; D002401:Cathepsin B / Q000302:isolation & purification; D002403:Cathepsins / Q000378:metabolism*; D002850:Chromatography, Gel; D008297:Male; D008970:Molecular Weight; D011817:Rabbits; D013737:Testis / Q000032:analysis*
chemical_list: D002403:Cathepsins; D002401:Cathepsin B