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

Buckwell, Stephen C., Page, Michael I., Waley, Stephen G. and Longridge, Jethro L. (1988) Hydrolysis of 7-substituted cephalosporins catalysed by ?-lactamases I and II from Bacillus cereus and by hydroxide ion. Journal of the Chemical Society, Perkin Transactions 2 (10). pp. 1815-1821. ISSN 1472-779X

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Abstract

Kinetic parameters are reported for the Bacillus cereus-lactamase I- and -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 -lactamase I, kcat/Km varies over 2 × 105 but for -lactamase II the variation with substituents is only 10. For alkyl substituents, kcat/Km increases with chain length and passes through a maximum, for -lactamase I this is with the undecyl derivative and for -lactamase II the octylcephalosporin. For -lactamase I, but not for -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 -lactamase I but not -lactamase II. It is suggested that a carboxy group on -lactamase I acts as a general catalyst facilitating -lactam C–N bond fission.

Item Type:	Article
Subjects:	Q Science > Q Science (General) Q Science > QD Chemistry
Schools:	School of Applied Sciences
Related URLs:	Author
Depositing User:	Sharon Beastall
Date Deposited:	06 Nov 2009 11:09
Last Modified:	06 Nov 2009 11:09
URI:	http://eprints.hud.ac.uk/id/eprint/6124

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