title: Cathepsin L--a latent proteinase in guinea pig sperm.
abstract: Guinea pig spermatozoa were found to contain a fully-latent cysteine proteinase that could be unmasked by incubating epididymal sperm for 2 hr at pH 3.5 and 37 degrees C. The proteinase was identified as cathepsin L (EC 3.4.22.15) on the basis of its optimal hydrolysis of benzyloxycarbonyl-Phe-Arg-7-(4-methyl)coumarylamide (Z-Phe-Arg-NMec) at pH 5.5; lack of action on Z-Arg-Arg-NMec and Arg-NMec; urea-enhanced digestion of azocasein; marked sensitivity to thiol reagents, leupeptin, Z-Phe-Phe-CHN2, and L-trans-epoxy-succinylleucylamido(3-methyl)butane (Ep-475 or E-64-c); and insensitivity to pepstatin and serine proteinase inhibitors. Gossypol, a male antifertility agent, was inhibitory. The unmasking phenomenon was reversibly inhibited by HgCl2 and mersalyl acid, and prevented by leupeptin and Ep-475, but not by pepstatin.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston 29425.
authors.forename: J K
authors.initials: JK
authors.lastname: McDonald
authors.forename: S
authors.initials: S
authors.lastname: Kadkhodayan
mesh_terms: D000818:Animals; D056668:Cathepsin L; D002403:Cathepsins / Q000302:isolation & purification / Q000378:metabolism*; D003546:Cysteine Endopeptidases; D004229:Dithiothreitol / Q000494:pharmacology; D010450:Endopeptidases; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D008627:Mercuric Chloride / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D013094:Spermatozoa / Q000201:enzymology*
chemical_list: D007976:Leupeptins; D011480:Protease Inhibitors; D008627:Mercuric Chloride; C032425:N-(N-(3-carboxyoxirane-2-carbonyl)leucyl)isoamylamine; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D056668:Cathepsin L; D007930:Leucine; D004229:Dithiothreitol