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The organophosphate-degrading enzyme from Agrobacterium radiobacter displays mechanistic flexibility for catalysis
Ely, Fernanda; Hadler, Kieran S.; Gahan, Lawrence R.; Guddat, Luke W.; Ollis, David L.; Schenk, Gerhard
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 hydrogenbond 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 theCo(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 theμOHis 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.
Keyword(s): Chemistry; Agrobacterium radiobacter; crystal structure; hydrogen bonding; OpdA; organophosphate-degrading enzyme; organophosphate pesticide; site-directed mutagenesis
Publication Date:
2010
Type: Journal article
Peer-Reviewed: Yes
Institution: Maynooth University
Citation(s): Ely, Fernanda and Hadler, Kieran S. and Gahan, Lawrence R. and Guddat, Luke W. and Ollis, David L. and Schenk, Gerhard (2010) The organophosphate-degrading enzyme from Agrobacterium radiobacter displays mechanistic flexibility for catalysis. Biochemical Journal, 432 (3). pp. 565-573. ISSN 0264-6021
Publisher(s): Portland Press
File Format(s): application/pdf
Related Link(s): http://mural.maynoothuniversity.ie/3677/1/GS_Organophosphate.pdf
First Indexed: 2020-01-31 06:06:23 Last Updated: 2020-04-02 07:27:30