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Electronic Structure Analysis of the Dinuclear Metal Center in the Bioremediator Glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes

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. (2010) Electronic Structure Analysis of the Dinuclear Metal Center in the Bioremediator Glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes. Inorganic Chemistry, 49. pp. 2727-2734. ISSN 0020-1669

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Abstract

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.

Item Type: Article
Additional Information: The definitive version of this article is available in Inorganic Chemistry, 2010, 49, pp.2727–2734, DOI: 10.1021/ic901950c
Keywords: Electronic Structure Analysis; Dinuclear Metal Center; Bioremediator; Glycerophosphodiesterase (GpdQ); Enterobacter aerogenes;
Subjects: Science & Engineering > Computer Science
Item ID: 3716
Depositing User: Gary Schenk
Date Deposited: 30 May 2012 16:14
Journal or Publication Title: Inorganic Chemistry
Publisher: American Chemical Society
Refereed: Yes
URI:

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