The OP (organophosphate)-degrading enzyme from Agrobacterium radiobacter (OpdA) is a binuclear metallohydrolase able to degrade highly toxic OP pesticides and nerve agents into less or non-toxic compounds. In the present study, the effect of metal ion substitutions and site-directed mutations on the catalytic properties of OpdA are investigated. The study shows the importance of both the metal ion composition and a hydrogen-bond network that connects the metal ion centre with the substrate-binding pocket using residues Arg254 and Tyr257 in the mechanism and substrate specificity of this enzyme. For the Co(II) derivative of OpdA two protonation equilibria (pKa1 ~5; pKa2 ~10) have been identified as relevant for catalysis, and a terminal hydroxide acts as the likely hydrolysis-initiating nucleophile. In contrast, the Zn(II) and Cd(II) derivatives only have one relevant protonation equilibrium (pKa ~4–5), and the μOH is the proposed nucleophile. The observed mechanistic flexibility may reconcile contrasting reaction models that have been published previously and may be beneficial for the rapid adaptation of OP-degrading enzymes to changing environmental pressures.
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Research Article|
November 25 2010
The organophosphate-degrading enzyme from Agrobacterium radiobacter displays mechanistic flexibility for catalysis
Fernanda Ely;
Fernanda Ely
*School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
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Kieran S. Hadler;
Kieran S. Hadler
*School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
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Lawrence R. Gahan;
Lawrence R. Gahan
*School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
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Luke W. Guddat;
Luke W. Guddat
*School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
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David L. Ollis;
David L. Ollis
†Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
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Gerhard Schenk
Gerhard Schenk
1
*School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
1To whom correspondence should be addressed (email schenk@uq.edu.au).
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Publisher: Portland Press Ltd
Received:
July 13 2010
Revision Received:
September 23 2010
Accepted:
September 24 2010
Accepted Manuscript online:
September 24 2010
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2010 Biochemical Society
2010
Biochem J (2010) 432 (3): 565–573.
Article history
Received:
July 13 2010
Revision Received:
September 23 2010
Accepted:
September 24 2010
Accepted Manuscript online:
September 24 2010
Citation
Fernanda Ely, Kieran S. Hadler, Lawrence R. Gahan, Luke W. Guddat, David L. Ollis, Gerhard Schenk; The organophosphate-degrading enzyme from Agrobacterium radiobacter displays mechanistic flexibility for catalysis. Biochem J 15 December 2010; 432 (3): 565–573. doi: https://doi.org/10.1042/BJ20101054
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