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Accueil > Publications > Recherche par années > Années 2000 > 2007

Badarau, A ; Damblon, C ; Page, MI

The activity of the dinuclear cobalt-ß-lactamase from Bacillus cereus in catalysing the hydrolysis of ß-lactams

Biochemical Journal 401 197-203

par Administrateur - publié le

Abstract :

Metallo-ß-lactamases are native zinc enzymes that catalyse the hydrolysis of ß-lactam antibiotics, but are also able to function with cobalt(II) and require one or two nnetal-ions for catalytic activity. The hydrolysis of cefoxitin, cephaloridine and benzylpenicillin catalysed by CoBcII (cobalt-substituted ß-lactamase from Bacillus cereus) 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 deprotionated form for metal-ion binding and catalysis. The species that results from the loss of one cobalt ion from the enzyme has no significant catalytic activity and is thought to be the mononuclear CoBcII. It appears that dinuclear CoBcII is the active form of the enzyme necessary for turnover, while the mononuclear CoBcII is only involved in substrate binding. The cobalt-substituted enzyme is a more efficient catalyst than the native enzyme for the hydrolysis of some ß-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 polarize the carbonyl group and stabilize the oxyanion tetrahedral intermediate.