title: Cathepsin L is capable of truncating cystatin C of 11 N-terminal amino acids.
abstract: Cystatin C with the 11 N-terminal amino acids truncated shows a much lower affinity for cysteine proteinases than the intact inhibitor. Such truncation of cystatin C is recorded after action of glycyl endopeptidase and cathepsin L. Incubation of cystatin C with papain, cathepsin B or cathepsin H led to no changes in the cystatin C molecule. Isoelectric focusing of the cathepsin L and cystatin C mixture showed the formation of two new bands. One of them appeared whether E-64 or PMSF was added or not, evidently representing a cystatin C/cathepsin L complex. The other band is the truncated cystatin C molecule. N-terminal sequencing after separation by HPLC showed that cystatin C is cleaved by cathepsin L at the Gly11-Gly12 bond. The action of cathepsin L on cystatin C may be explained by the cleavage of the scissile bond in an inappropriate complex.
authors.affiliation: Department of Biochemistry and Molecular Biology, Institute Jozef Stefan, Ljubljana, Slovenia.
authors.forename: T
authors.initials: T
authors.lastname: Popovic
authors.forename: N
authors.initials: N
authors.lastname: Cimerman
authors.forename: I
authors.initials: I
authors.lastname: Dolenc
authors.forename: A
authors.initials: A
authors.lastname: Ritonja
authors.forename: J
authors.initials: J
authors.lastname: Brzin
mesh_terms: D000595:Amino Acid Sequence; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D055316:Cystatin C; D015891:Cystatins / Q000737:chemistry / Q000378:metabolism*; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D006801:Humans; D007525:Isoelectric Focusing; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D011994:Recombinant Proteins; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L