Hadler, Kieran S. and Mitic, Natasa and Yip, Sylvia Hsu-Chen and Gahan, Lawrence R. and Ollis, David L. and Schenk, Gerhard and Larrabee, James A.
Electronic Structure Analysis of the Dinuclear Metal Center in the Bioremediator
Glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes.
Inorganic Chemistry, 49.
The glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes is a promiscuous, dinuclear metallohydrolase
that has potential application in the remediation of organophosphate nerve agents and pesticides. GpdQ employs an
unusual reaction mechanism in which the enzyme is predominantly mononuclear in the resting state, and substrate
binding induces the formation of the catalytically competent dinuclear center (Hadler et al. J. Am. Chem. Soc. 2008,
130, 14129). Reactivity is further modulated by the coordination flexibility of Asn80, a ligand that binds to the second,
loosely bound metal ion (Hadler et al. J. Am. Chem. Soc. 2009, 131, 11900). It is proposed that hydrolysis is initiated by
a terminal, metal-bound hydroxide molecule which is activated at unusually low pH by electrostatic/hydrogen bonding
interactions with a bridging hydroxide species. In this study, electronic structure analysis of the dinuclear center is
employed to study the coordination environment of the dinuclear center at the resting and product-bound stage of
catalysis. This is achieved through the use of variable temperature, variable field magnetic circular dichroism
experiments involving the Co(II)-substituted wild type enzyme and its Asn80Asp variant. The data support the above
model for the catalytic mechanism whereby the metal ion-bridging hydroxide molecule activates a terminally bound
hydroxide nucleophile. Replacement of Asn80 by an aspartate residue does prevent coordination flexibility but also
leads to cleavage of the μ-hydroxide bridge and reduced reactivity. This is the first study to investigate the electronic
structure of an enzyme with a μ-1,1-carboxylate bridged dicobalt(II) center.
||The definitive version of this article is available in Inorganic Chemistry, 2010, 49, pp.2727–2734, DOI: 10.1021/ic901950c
||Electronic Structure Analysis; Dinuclear Metal Center; Bioremediator;
Glycerophosphodiesterase (GpdQ); Enterobacter aerogenes;
||Science & Engineering > Computer Science
||30 May 2012 16:14
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||American Chemical Society
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