Metallo-β-lactamases are native zinc enzymes that catalyse the hydrolysis of β-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 CoBcII (cobalt-substituted β-lactamase from Bacillus cereus) has been studied at different pHs and metal-ion concentrations. An enzyme group of pKa 6.52±0.1 is found to be required in its deprotonated 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 β-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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Research Article|
December 11 2006
The activity of the dinuclear cobalt-β-lactamase from Bacillus cereus in catalysing the hydrolysis of β-lactams
Adriana Badarau;
Adriana Badarau
*Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
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Christian Damblon;
Christian Damblon
†Biological NMR Centre, Department of Biochemistry, Henry Wellcome Building, Lancaster Road, University of Leicester, Leicester LE1 9HN, U.K.
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Michael I. Page
Michael I. Page
1
*Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
1To whom correspondence should be addressed (email m.i.page@hud.ac.uk).
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Publisher: Portland Press Ltd
Received:
June 29 2006
Revision Received:
August 24 2006
Accepted:
September 11 2006
Accepted Manuscript online:
September 11 2006
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2007
Biochem J (2007) 401 (1): 197–203.
Article history
Received:
June 29 2006
Revision Received:
August 24 2006
Accepted:
September 11 2006
Accepted Manuscript online:
September 11 2006
Citation
Adriana Badarau, Christian Damblon, Michael I. Page; The activity of the dinuclear cobalt-β-lactamase from Bacillus cereus in catalysing the hydrolysis of β-lactams. Biochem J 1 January 2007; 401 (1): 197–203. doi: https://doi.org/10.1042/BJ20061002
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