The organophosphate-degrading enzyme from Agrobacterium radiobacter displays mechanistic flexibility for catalysis

Fernanda Ely, Kieran S. Hadler, Lawrence R. Gahan, Luke W. Guddat, David L. Ollis, Gerhard Schenk*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    70 Citations (Scopus)

    Abstract

    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 Arg 254 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.

    Original languageEnglish
    Pages (from-to)565-573
    Number of pages9
    JournalBiochemical Journal
    Volume432
    Issue number3
    DOIs
    Publication statusPublished - 15 Dec 2010

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