Reference : The activity of the dinuclear cobalt-beta-lactamase from Bacillus cereus in catalysin...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
The activity of the dinuclear cobalt-beta-lactamase from Bacillus cereus in catalysing the hydrolysis of beta-lactams
Badarau, Adriana [> > > >]
Damblon, Christian mailto [Université de Liège - ULiège > Département de chimie (sciences) > Chimie biologique structurale >]
Page, Michael I [> > > >]
Biochemical Journal
Portland Press
Part 1
Yes (verified by ORBi)
United Kingdom
[en] Bacillus cereus ; cobalt substitution ; beta-lactan hydrolysis ; metallo-beta-lactamase ; pH-rate profile
[en] 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 nnetal-ions for catalytic activity. The hydrolysis of cefoxitin, cephaloridine and benzylpenicillin catalysed by CoBcII (cobalt-substituted beta-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 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 polarize the carbonyl group and stabilize the oxyanion tetrahedral intermediate.

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