The activity of the dinuclear cobalt-{beta}-lactamase from Bacillus cereus in catalysing the hydrolysis of {beta}-lactams

Adriana Badarau , Christian Damblon , Michael I Page (1)

1 Chemical and Biological Sciences

Metallo-{beta}-lactamases are native zinc enzymes that catalyse the hydrolysis of {beta}-lactam antibiotics, but are also able to function with cobalt (II) and require one or two metal-ions for catalytic activity. The hydrolysis of cefoxitin, cephaloridine and benzylpenicillin catalysed by cobalt substituted {beta}-lactamase from Bacillus cereus (BcII) has been studied at different pHs and metal-ion concentrations. An enzyme group of pK a} 6.52±0.1 is found to be required in its deprotonated form for metal-ion binding and catalysis. The species that resulted from the loss of one cobalt ion from the enzyme has no significant catalytic activity and is thought to be the mono-nuclear CoBcII. It appears that di-nuclear CoBcII is the active form of the enzyme necessary for turnover, while the mono-nuclear CoBcII is only involved in substrate binding. The cobalt enzyme is a more efficient catalyst than the native zinc enzyme for the hydrolysis of some {beta}-lactam antibiotics suggesting that the role of the metal-ion is predominantly to provide the nucleophilic hydroxide, rather than to act as a Lewis acid to polarise the carbonyl group and stabilise the oxyanion tetrahedral intermediate.

Mots clés: Life Sciences

Adriana Badarau, Christian Damblon, Michael I Page. The activity of the dinuclear cobalt-{beta}-lactamase from Bacillus cereus in catalysing the hydrolysis of {beta}-lactams. Biochemical Journal, 2006, 401 (1), pp.197-203. ⟨10.1042/BJ20061002⟩. ⟨hal-00478624⟩