Single-turnover and steady-state kinetics of hydrolysis of cephalosporins by beta-lactamase I from Bacillus cereus.
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ABSTRACT: The kinetics of the hydrolysis of two cephalosporins by beta-lactamase I from Bacillus cereus 569/H/9 has been studied by single-turnover and steady-state methods. Single-turnover kinetics could be measured over the time scale of minutes when cephalosporin C was the substrate. The other substrate, 7-(2',4'-dinitrophenylamino)deacetoxycephalosporanic acid, was hydrolysed even more slowly, and has potential for use in crystallographic studies of beta-lactamases. Comparison of single-turnover and steady-state kinetics showed that, for both substrates, opening the beta-lactam ring (i.e. acylation of the enzyme) was the rate-determining step. Thus the non-covalent enzyme-substrate complex is expected to be the intermediate observed crystallographically.
SUBMITTER: Bicknell R
PROVIDER: S-EPMC1152706 | biostudies-other | 1985 Oct
REPOSITORIES: biostudies-other
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