Role of zinc content on the catalytic efficiency of B1 metallo-beta-lactamases

M. DAL PERARO, A.J.VILA, P.CARLONI AND M. L.KLEIN

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

ACS

Lugar: Columbus, OH, Estados Unidos; Año: 2007 vol. 129 p. 2808 - 2816

0002-7863

Metallo beta-lactamases (MBL) are enzymes naturally evolved by bacterial strains under theevolutionary pressure of beta-lactam antibiotic clinical use. They have a broad substrate spectrum and are resistant to all the clinically useful inhibitors, representing a potential risk of infection if massively disseminated. The MBL scaffold is designed to accommodate one or two zinc ions able to activate a nucleophilic hydroxide for the hydrolysis of the â-lactam ring. The role of zinc content on the binding and reactive mechanism of action has been the subject of debate and still remains an open issue despite the large amount of data acquired. We report herein a study of the reaction pathway for binuclear CcrA from Bacteroides fragilis using density functional theory based quantum mechanics-molecular mechanics dynamical modeling. CcrA is the prototypical binuclear enzyme belonging to the B1 MBL family, which includes several harmful chromosomally encoded and transferable enzymes. The involvement of a second zinc ion in the catalytic mechanism lowers the energetic barrier for beta-lactam hydrolysis, preserving the essential binding features found in mononuclear B1 enzymes (BcII from Bacillus cereus) while providing amore efficient single-step mechanism. Overall, this study suggests that uptake of a second equivalent zinc ion is evolutionary favored.