title: A survey of the kinetic parameters of class C beta-lactamases. Cephalosporins and other beta-lactam compounds.
abstract: Various cephalosporins, cefoxitin, moxalactam, imipenem and aztreonam were studied as substrates of six class C beta-lactamases. Nitrocefin, cephaloridine, cefazolin, cephalothin and cephalexin were good substrates, with kcat. values ranging from 27 to 5000 s-1. Cefuroxime, cefotaxime and cefoxitin exhibited low kcat. values (0.010-1.7 s-1) and low Km values, which suggested a rate-limiting deacylation. Imipenem and aztreonam were even poorer substrates (kcat. 2 x 10(-4)-3 x 10(-2) s-1) and, in the presence of a reporter substrate, behaved as transient inactivators. With moxalactam, biphasic kinetics were observed, indicating a possible rearrangement of the acyl-enzyme.
authors.affiliation: Laboratoire d'Enzymologie, Université de Liège, Sart Tilman, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Galleni
authors.forename: G
authors.initials: G
authors.lastname: Amicosante
authors.forename: J M
authors.initials: JM
authors.lastname: Frère
mesh_terms: D001398:Aztreonam / Q000378:metabolism; D002511:Cephalosporins / Q000378:metabolism*; D006868:Hydrolysis; D015378:Imipenem / Q000378:metabolism; D007700:Kinetics; D009070:Moxalactam / Q000378:metabolism; D013379:Substrate Specificity; D001618:beta-Lactamases / Q000145:classification / Q000378:metabolism*
chemical_list: D002511:Cephalosporins; D015378:Imipenem; D001618:beta-Lactamases; D001398:Aztreonam; D009070:Moxalactam