title: Kinetic study of two novel enantiomeric tricyclic beta-lactams which efficiently inactivate class C beta-lactamases.
abstract: A detailed kinetic study of the interaction between two ethylidene derivatives of tricyclic carbapenems, Lek 156 and Lek 157, and representative beta-lactamases and D-alanyl-D-alanine peptidases (DD-peptidases) is presented. Both compounds are very efficient inactivators of the Enterobacter cloacae 908R beta-lactamase, which is usually resistant to inhibition. Preliminary experiments indicate that various extended-spectrum class C beta-lactamases (ACT-1, CMY-1, and MIR-1) are also inactivated. With the E. cloacae 908R enzyme, complete inactivation occurs with a second-order rate constant, k(2)/K', of 2 x 10(4) to 4 x 10(4) M(-1) s(-1), and reactivation is very slow, with a half-life of >1 h. Accordingly, Lek 157 significantly decreases the MIC of ampicillin for E. cloacae P99, a constitutive class C beta-lactamase overproducer. With the other serine beta-lactamases tested, the covalent adducts exhibit a wide range of stabilities, with half-lives ranging from long (>4 h with the TEM-1 class A enzyme), to medium (10 to 20 min with the OXA-10 class D enzyme), to short (0.2 to 0.4 s with the NmcA class A beta-lactamase). By contrast, both carbapenems behave as good substrates of the Bacillus cereus metallo-beta-lactamase (class B). The Streptomyces sp. strain R61 and K15 extracellular DD-peptidases exhibit low levels of sensitivity to both compounds.
authors.affiliation: Laboratoire d'Enzymologie, Centre for Protein Engineering, University of Liège, Institut de Chimie, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Vilar
authors.forename: M
authors.initials: M
authors.lastname: Galleni
authors.forename: T
authors.initials: T
authors.lastname: Solmajer
authors.forename: B
authors.initials: B
authors.lastname: Turk
authors.forename: J M
authors.initials: JM
authors.lastname: Frère
authors.forename: A
authors.initials: A
authors.lastname: Matagne
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D015780:Carbapenems / Q000737:chemistry / Q000494:pharmacology*; D004347:Drug Interactions; D016972:Enterobacter cloacae / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010406:Penicillins / Q000494:pharmacology; D013302:Streptomyces / Q000187:drug effects / Q000201:enzymology; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D065093:beta-Lactamase Inhibitors
chemical_list: D015780:Carbapenems; D004791:Enzyme Inhibitors; D010406:Penicillins; D065093:beta-Lactamase Inhibitors; D000667:Ampicillin; D002267:Muramoylpentapeptide Carboxypeptidase