title: Cathepsins X and B display distinct activity profiles that can be exploited for inhibitor design.
abstract: The carboxypeptidase and endopeptidase activities of cathepsins X and B, as well as their inhibition by E-64 derivatives, have been investigated in detail and compared. The results clearly demonstrate that cathepsins X and B do not share similar activity profiles against substrates and inhibitors. Using quenched fluorogenic substrates, we show that cathepsin X preferentially cleaves substrates through a monopeptidyl carboxypeptidase pathway, while cathepsin B displays a preference for the dipeptidyl pathway. The preference for one or the other pathway is about the same for both enzymes, i. e. approximately 2 orders of magnitude. Cleavage of a C-terminal dipeptide of a substrate by cathepsin X can be observed under conditions that preclude efficient monopeptidyl carboxypeptidase activity. In addition, an inhibitor designed to exploit the unique structural features responsible for the carboxypeptidase activity of cathepsin X has been synthesized and tested against cathepsins X, B and L. Although of moderate potency, this E-64 derivative is the first reported example of a cathepsin X-specific inhibitor. By comparison, CA074 was found to inactivate cathepsin B at least 34000-fold more efficiently than cathepsin X.
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec.
authors.forename: R
authors.initials: R
authors.lastname: Ménard
authors.forename: C
authors.initials: C
authors.lastname: Therrien
authors.forename: P
authors.initials: P
authors.lastname: Lachance
authors.forename: T
authors.initials: T
authors.lastname: Sulea
authors.forename: H
authors.initials: H
authors.lastname: Qo
authors.forename: A D
authors.initials: AD
authors.lastname: Alvarez-Hernandez
authors.forename: W R
authors.initials: WR
authors.lastname: Roush
mesh_terms: D002401:Cathepsin B / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D056657:Cathepsin K; D002403:Cathepsins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D020689:Exopeptidases / Q000378:metabolism; D005456:Fluorescent Dyes; D006801:Humans; D007930:Leucine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D008956:Models, Chemical; D013379:Substrate Specificity
chemical_list: D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D002403:Cathepsins; D020689:Exopeptidases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534130:CTSK protein, human; D056657:Cathepsin K; D007930:Leucine; C024974:E 64