Author(s): Schofield DA, Dinovo AA
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Abstract AIMS: The bacterial organophosphorus hydrolase (OPH) enzyme hydrolyses and detoxifies a broad range of toxic organophosphate pesticides and warfare nerve agents by cleaving the various phosphorus-ester bonds (P-O, P-F, P-CN, P-S); however, OPH hydrolyses these bonds with varying efficiencies. The aim of this study was to generate a variant OPH enzyme with improved hydrolytic efficiency against the poorly hydrolysed P-S class of organophosphates. METHODS AND RESULTS: The gene encoding OPH was sequentially mutated at specific codons by saturation mutagenesis and screened for improved activity against the P-S substrates demeton-S methyl and malathion. Escherichia coli lysates harbouring the variants displayed up to 177- and 1800-fold improvement in specific activity against demeton-S methyl and malathion, respectively, compared to the wild-type lysates. The specificity constants of the purified variant proteins were improved up to 25-fold for demeton-S methyl and malathion compared to the wild-type. Activity was associated with organophosphate detoxification as the hydrolysed substrate lost the ability to inhibit acetylcholinesterase. The improved hydrolytic efficiency against demeton-S translated to the improved ability to hydrolyse the warfare agent VX. CONCLUSIONS: OPH variant enzymes were generated that displayed significantly improved ability to hydrolyse and detoxify organophosphates harbouring the P-S bond. SIGNIFICANCE AND IMPACT OF THE STUDY: The long-term goal is to generate an environmentally-friendly enzyme-mediated bioremediation approach for the removal of toxic organophosphate compounds in the environment.
This article was published in J Appl Microbiol
and referenced in Journal of Bioremediation & Biodegradation