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  • Title: Interaction of beta-lactamases I and II from Bacillus cereus with semisynthetic cephamycins. Kinetic studies.
    Author: Martin Villacorta J, Arriaga P, Laynez J, Menendez M.
    Journal: Biochem J; 1991 Oct 01; 279 ( Pt 1)(Pt 1):111-4. PubMed ID: 1930129.
    Abstract:
    The influence of C-6 alpha- or C-7 alpha-methoxylation of the beta-lactam ring in the catalytic action of class A and B beta-lactamases has been investigated. For this purpose the kinetic behaviour of beta-lactamases I (class A) and II (class B) from Bacillus cereus was analysed by using several cephamycins, moxalactam, temocillin and related antibiotics. These compounds behaved as poor substrates for beta-lactamase II, with high Km values and very low catalytic efficiencies. In the case of beta-lactamase I, the substitution of a methoxy group for a H atom at C-7 alpha or C-6 alpha decreased the affinity of the substrates for the enzyme. Furthermore, the acylation of cephamycins was completely blocked, whereas that of penicillins was slowed down by a factor of 10(4)-10(5), acylation being the rate-determining step of the process.
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