Epoxide forming and degrading enzymes in the spider mite, Tetranychus urticae

1. Enzymes associated with the epoxidation and epoxide hydration or glutathione conjugation pathway occurred in the herbivorous mite, Tetranychus urticae. 2. Epoxidation of aldrin was primarily microsomal, required NADPH, was associated with a NADPH-cytochrome c reductase, and was inhibited by CO, 1-phenylimidazole and piperonyl butoxide. 3. Trans- and cis-epoxide hydrolases resided mostly in the microsomal fraction but were localized also in the cytosol. These activities were differentially inhibited by l,2-epoxy-3,3,3-trichloropropane, and chalcone and 4-phenylchalcone oxides. 4. In vitro and in vivo rates of aldrin epoxidation were very similar indicating that in vitro artifacts were not impairing full enzyme measurement. This was further confirmed in experiments with enzyme stabilizers.