nitrocefin has been researched along with 6-iodopenicillanic-acid* in 1 studies
1 other study(ies) available for nitrocefin and 6-iodopenicillanic-acid
Article | Year |
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Beta-lactamases as fully efficient enzymes. Determination of all the rate constants in the acyl-enzyme mechanism.
The rate constants for both acylation and deacylation of beta-lactamase PC1 from Staphylococcus aureus and the RTEM beta-lactamase from Escherichia coli were determined by the acid-quench method [Martin & Waley (1988) Biochem. J. 254, 923-925] with several good substrates, and, for a wider range of substrates, of beta-lactamase I from Bacillus cereus. The values of the acylation and deacylation rate constants for benzylpenicillin were approximately the same (i.e. differing by no more than 2-fold) for each enzyme. The variation of kcat./Km for benzylpenicillin with the viscosity of the medium was used to obtain values for all four rate constants in the acyl-enzyme mechanism for all three enzymes. The reaction is partly diffusion-controlled, and the rate constant for the dissociation of the enzyme-substrate complex has approximately the same value as the rate constants for acylation and deacylation. Thus all three first-order rate constants have comparable values. Here there is no single rate-determining step for beta-lactamase action. This is taken to be a sign of a fully efficient enzyme. Topics: Acylation; Bacillus cereus; beta-Lactamase Inhibitors; beta-Lactamases; Cephalosporins; Chemical Phenomena; Chemistry; Deuterium; Escherichia coli; Hydrolysis; Kinetics; Penicillanic Acid; Penicillin G; Staphylococcus aureus; Substrate Specificity | 1990 |