A cloned bacterial enzyme for nerve agent decontamination

Organophosphorus acid (OPA) anhydrolases offer considerable potential for safe, non-corrosive decontamination of chemical nerve agents. The Alteromonas sp. strain JD6.5 gene encoding an OPA anhydrolase (designated as OPAA-2), which hydrolyzes a wide variety of nerve agents, has been cloned in Escherichia coli. Employing agent-analog diisopropyl fluorophosphate (DFP) as a substrate, the effects of buffers, pH, temperature, and various protein stabilizing agents on OPAA-2 activity were studied. Ammonium carbonate, which is innocuous and inexpensive, proved to be a superior buffer for enzyme activity. Compared with enzyme assayed under standard conditions, enzyme activity with ammonium carbonate was six-fold greater. To evaluate effects of storage and reconstitution on enzyme activity, the cloned enzyme was lyophilized, rehydrated, and then assessed by measuring activity against DFP. Whereas almost 100% of the hydrolytic activity was recovered with enzyme reconstituted in (NH₄)₂CO₃-buffered distilled water or chlorinated drinking water, approximately 20% of the activity was recovered with ocean water. Enzyme stability in blast-containment foam or fire-fighting foam was also demonstrated by high activity in (NH₄)₂CO₃-buffered distilled water or drinking water. These findings suggest the potential of a foam-based enzyme system for field decontamination of chemical nerve agents.