title: Proteolytically active complexes of cathepsin L and a cysteine proteinase inhibitor; purification and demonstration of their formation in vitro.
abstract: Proteolytically active complexes of the proteinase cathepsin L, with an endogenous inhibitor of cysteine proteinases, were purified from sheep liver. The complexes were active against the synthetic substrate Z-Phe-Arg-NHMec and also the proteins azocasein and gelatin. The composition of the complexes was demonstrated by Western blotting, after reducing and nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis with monospecific antibodies raised against purified sheep liver cathepsin L and purified sheep liver cysteine proteinase inhibitor (probably stefin B). Similar complexes could be formed in vitro, by coincubation of purified sheep liver cathepsin L with the purified sheep liver cystatin at a pH of 5.5 or higher.
authors.affiliation: Department of Biochemistry, University of Natal, Pietermaritzburg, South Africa.
authors.forename: R N
authors.initials: RN
authors.lastname: Pike
authors.forename: T H
authors.initials: TH
authors.lastname: Coetzer
authors.forename: C
authors.initials: C
authors.lastname: Dennison
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D056668:Cathepsin L; D002403:Cathepsins / Q000302:isolation & purification / Q000378:metabolism*; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D015891:Cystatins / Q000302:isolation & purification / Q000378:metabolism*; D003546:Cysteine Endopeptidases; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D046911:Macromolecular Substances; D008954:Models, Biological; D008970:Molecular Weight; D011485:Protein Binding; D012756:Sheep; D013379:Substrate Specificity
chemical_list: D015891:Cystatins; D046911:Macromolecular Substances; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D056668:Cathepsin L