Is there a Multiple Pesticide Metabolizing Cytochrome P450 in Maize?

Abstract

Cytochrome P450 monooxygenases (P450) were long considered to be a potentially important enzyme system for the detoxification of herbicides in maize and other crop plants. Only recently has herbicide metabolism by P450 in maize microsomes been conclusively demonstrated. Fourteen herbicides in six chemical families have been shown to be metabolized by P450 in maize. Herbicides demonstrated as metabolized by P450 in maize include bentazon, chlortoluron, linuron, acetochlor, metolachlor, flumetsulam, CGA152005, chlorimuron-ethyl, chlorsulfuron, nicosulfuron, primisulfuron, triasulfuron, imazethapyr, and AC 263,222. Reactions with the herbicides catalyzed by P450 include a number of ring hydroxylations, alkyl hydroxylations and N and O demethylations. These are all typical P450 reactions. In addition to the herbicides discussed, organophosphate insecticides (diazinon and malathion) are desulfurated by P450 in corn microsomes. The desulfurated metabolites are actually the active insect toxicant. This is the same reaction that can occur in insects and mammals. P450 is now considered of equal importance to glutathione-S-transferases (GST) for the metabolism of herbicides in maize.