121003-44-9Relevant articles and documents
Hydrolysis of 7-Substituted Cephalosporins catalysed by β-Lactamase I and II from Bacillus cereus and by Hydroxide Ion
Buckwell, Stephen C.,Page, Michael I.,Waley, Stephen G.,Longridge, Jethro L.
, p. 1815 - 1822 (2007/10/02)
Kinetic parameters are reported for the Bacillus cereus β-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 2x105 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.
