Various cephalosporins, cefoxitin, moxalactam, imipenem and aztreonam were studied as substrates of six class C β-lactamases. Nitrocefin, cephaloridine, cefazolin, cephalothin and cephalexin were good substrates, with k(cat.) values ranging from 27 to 5000 s-1. Cefuroxime, cefotaxime and cefoxitin exhibited low k(cat.) values (0.010-1.7 s-1) and low K(m) values, which suggested a rate-limiting deacylation. Imipenem and aztreonam were even poorer substrates (k(cat.) 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.
A survey of the kinetic parameters of class C β-lactamases. Cephalosporins and other β-lactam compounds
AMICOSANTE, Gianfranco;
1988-01-01
Abstract
Various cephalosporins, cefoxitin, moxalactam, imipenem and aztreonam were studied as substrates of six class C β-lactamases. Nitrocefin, cephaloridine, cefazolin, cephalothin and cephalexin were good substrates, with k(cat.) values ranging from 27 to 5000 s-1. Cefuroxime, cefotaxime and cefoxitin exhibited low k(cat.) values (0.010-1.7 s-1) and low K(m) values, which suggested a rate-limiting deacylation. Imipenem and aztreonam were even poorer substrates (k(cat.) 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.Pubblicazioni consigliate
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