Chloroperoxidase-mediated oxidation of organophosphorus pesticides

Chloroperoxidase from Caldariomyces fumago was tested for the oxidation of 10 organophosphorus pesticides. Organophosphorus pesticides containing the phosphorothioate group, azinphos-methyl, chlorpyrifos, dichlorofenthion, dimethoate, parathion, phosmet, and terbufos were oxidized by chloroperoxidase in the presence of hydrogen peroxide and chloride ions. The products were identified as oxon derivatives (phosphates), where the sulfur atom from the thioate group is substituted by an oxygen atom. No hydrolysis products were detected after enzymatic oxidation of these pesticides, and no halogenation of substrates was detected. Chloroperoxidase oxidation of relatively toxic organophosphorus pesticides produces metabolites similar to those formed by cytochrome P450 during the metabolic activation of pesticides in vivo. However, the major difference between these biocatalysts is that further cleavage of oxons, which is typical of the P450-catalyzed reaction, was not observed with Chloroperoxidase.