Issue 10, 1988

Hydrolysis of 7-substituted cephalosporins catalysed by β-lactamases I and II from Bacillus cereus and by hydroxide ion

Abstract

Kinetic parameters are reported for the Bacillus cereusβ-lactamase I- and β-lactamase II-catalysed hydrolysis of a series of thirty-seven cephalosporins substituted in the 7-position. These are compared with the second-order rate constants for the hydroxide ion-catalysed hydrolysis of these derivatives. There is no significant dependence of the rate of the base-catalysed hydrolysis upon the nature of the side-chain substituent. For β-lactamase I, kcat/Km varies over 2 × 105 but for β-lactamase II the variation with substituents is only 10. For alkyl substituents, kcat/Km increases with chain length and passes through a maximum, for β-lactamase I this is with the undecyl derivative and for β-lactamase II the octylcephalosporin. For β-lactamase I, but not for β-lactamase II, the t-butylcephalosporin is a very poor substrate. There is no evidence for a significant cavity in either enzyme to host aromatic residues. An ionised carboxylate residue on the side-chain significantly reduces reactivity with β-lactamase I but not β-lactamase II. It is suggested that a carboxy group on β-lactamase I acts as a general catalyst facilitating β-lactam C–N bond fission.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1988, 1815-1821

Hydrolysis of 7-substituted cephalosporins catalysed by β-lactamases I and II from Bacillus cereus and by hydroxide ion

S. C. Buckwell, M. I. Page, S. G. Waley and J. L. Longridge, J. Chem. Soc., Perkin Trans. 2, 1988, 1815 DOI: 10.1039/P29880001815

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