121002-87-7Relevant academic research and scientific papers
Hydrolysis of 3-Substituted Cephalosporins catalysed by β-Lactamases I and II from Bacillus cereus and by Hydroxide Ion
Buckwell, Stephen C.,Page, Michael I.,Longridge, Jethro L.,Waley, Stephen G.
, p. 1823 - 1828 (2007/10/02)
Second-order rate constants for the alkaline hydrolysis of 3-thiol substituted cephalosporins are independent of the pKa of the thiol over a pKa range of 9.If there is a leaving group at C-3' it is expelled after the β-lactam ring is opened and the expulsion of the leaving group does not enhance the rate of β-lactam C-N bond fission.The zinc enzyme β-lactamase II is about a 100-fold better catalyst than the serine enzyme β-lactamase I for the hydrolysis of the same cephalosporin.The second-order rate constant kcat/Km for both β-lactamase enzymes shows no dependence on the nature of the substituent at C-3' which is not explicable by the different chemical reactivity of the cephalosporins.There is no evidence for a significant recognition site in either enzyme for the C-3' substituent.The kinetic parameters kcat and Km for the β-lactamase I-catalysed hydrolysis may be complicated by the formation of intermediates.
