title: Inactivation of Bacillus cereus beta-lactamase by halogenated isoxazolylpenicillins.
abstract: Upon preincubation with halogenated isoxazolyl-penicillins, the activity of Bacillus cereus beta-lactamase is decreased by a factor proportional to the inhibitor concentration. This inactivation, which concerns essentially the catalytic rate constant of the enzyme, occurs only at or above 37 degrees C with cloxacillin and dicloxacillin, and even at 25 degrees C with flucloxacillin. The dependence of the inactivation rate upon inhibitor concentration is consistent, in the former case, with the occurrence of a bimolecular reaction, and in the latter case, with a bimolecular process followed by a monomolecular step.
mesh_terms: D001409:Bacillus cereus / Q000187:drug effects / Q000201:enzymology*; D004009:Dicloxacillin / Q000494:pharmacology; D007555:Isoxazoles / Q000494:pharmacology*; D007700:Kinetics; D008433:Mathematics; D010080:Oxazoles / Q000494:pharmacology*; D010406:Penicillins / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013696:Temperature; D013997:Time Factors; D065093:beta-Lactamase Inhibitors
chemical_list: D007555:Isoxazoles; D010080:Oxazoles; D010406:Penicillins; D065093:beta-Lactamase Inhibitors; D004009:Dicloxacillin