Acephate is an important systemic organophosphorus insecticide with toxicity attributed to bioactivation on metabolic conversion to methamidophos (or an oxidized metabolite thereof) which acts as an acetylcholinesterase (AChE) inhibitor. The selective toxicity of acephate is considered to be due to facile conversion to methamidophos in insects but not mammals. We show in the present investigation that a carboxyamidase activates acephate in mice ...