title: Kinetics of the reaction between 5,5'-dithiobis[2-nitrobenzoic acid] and the sulphydryl group in Zn(2+)-dependent beta-lactamase II.
abstract: The kinetics of the reaction of the thiol residue in Zn(2+)-dependent beta-lactamase II with 5,5'-dithiobis[2-nitrobenzoic acid], and the concomitant inactivation revealed that both events take place at the same rate. The inactivation could not be reverted by incubation with Zn2+ or by using a substrate concentration about eight times the Km of the enzyme. EDTA incubation also produced inactivation of the enzyme, although it was reverted by increasing the substrate concentration in the assay. A dual role is proposed for Zn2+ in beta-lactamase. The kinetic analysis of the thiol modification and the concomitant inactivation is in agreement with previous reports on the implication of the metal ion in catalysis. A role in stabilizing the native structure of the enzyme is also suggested.
authors.affiliation: Departamento de Quimica Fisica Aplicada, Universidad Autónoma de Madrid, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Benitez
authors.forename: M
authors.initials: M
authors.lastname: Company
authors.forename: J S
authors.initials: JS
authors.lastname: Jimènez
mesh_terms: D001407:Bacillus / Q000201:enzymology; D002510:Cephalosporinase / Q000737:chemistry* / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D007700:Kinetics; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: D004228:Dithionitrobenzoic Acid; D002510:Cephalosporinase; D015032:Zinc