title: Kinetics of inactivation of beta-lactamase I by 6 beta-bromopenicillanic acid.
abstract: The kinetics of the inactivation of beta-lactamase I from Bacillus cereus 569 by preparations of 6 alpha-bromopenicillanic acid showed unexpected features. These can be quantitatively accounted for on the basis of the inactivator being the epimer, 6 beta-bromopenicillanic acid. At pH 9.2, the rate-determining step in the inactivation is the formation of the inactivator. When pure 6 beta-bromopenicillanic acid is used to inactivate beta-lactamase I, simple second-order kinetics are observed. The inactivated enzyme has a new absorption peak at 326 nm. The rate constant for inactivation has the same value as the rate constant for appearance of absorption at 326 nm; the rate-determining step may thus be fission of the beta-lactam ring of 6 beta-bromopenicillanic acid. Inactivation is slower in the presence of substrate, and the observed kinetics can be quantitatively accounted for on a simple competitive model. The results strongly suggest that inactivation is a consequence of reaction at the active site.
mesh_terms: D001409:Bacillus cereus / Q000201:enzymology; D007700:Kinetics; D008433:Mathematics; D010397:Penicillanic Acid / Q000494:pharmacology* / Q000031:analogs & derivatives; D011485:Protein Binding; D013056:Spectrophotometry, Ultraviolet; D065093:beta-Lactamase Inhibitors
chemical_list: D065093:beta-Lactamase Inhibitors; C018008:brobactam; D010397:Penicillanic Acid