title: Human cathepsin B is a metastable enzyme stabilized by specific ionic interactions associated with the active site.
abstract: The effect of neutral or alkaline pH on cathepsin B activity and structure was investigated. An irreversible loss of activity, accompanied by large structural changes, was observed at pH > or = 7.0. The high activation energy of 183.5 kJ mol-1, calculated for the inactivation process, is in good agreement with structural changes observed by circular dichroism. Both the pH-induced inactivation and the pH-induced unfolding of cathepsin B were found to be first-order processes, exponentially increasing with increasing pH of the solution. The good agreement of the rate constants of inactivation and unfolding of the enzyme indicates an important structure-function relationship. Cathepsin B was also found to be destabilized both by increasing ionic strength and organic solvent content.
authors.affiliation: Department of Biochemistry and Molecular Biology, J. Stefan Institute, Ljubljana, Slovenia.
authors.forename: B
authors.initials: B
authors.lastname: Turk
authors.forename: I
authors.initials: I
authors.lastname: Dolenc
authors.forename: E
authors.initials: E
authors.lastname: Zerovnik
authors.forename: D
authors.initials: D
authors.lastname: Turk
authors.forename: F
authors.initials: F
authors.lastname: Gubensek
authors.forename: V
authors.initials: V
authors.lastname: Turk
mesh_terms: D001665:Binding Sites; D002401:Cathepsin B / Q000737:chemistry*; D002942:Circular Dichroism; D004795:Enzyme Stability; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009994:Osmolar Concentration; D011487:Protein Conformation; D013154:Spleen / Q000201:enzymology; D013696:Temperature
chemical_list: D002401:Cathepsin B