Interactions of various agrochemicals with cytochrome P-450-dependent monooxygenases of wheat cells

Abstract

Levels of cytochrome P-450s and rates of monooxygenase activities were studied in microsomes prepared from wheat cell suspension cultures. Cytochrome contents and enzymatic activities, namely, the enzymatic systems responsible for chlorotoluron ring-methyl hydroxylation and N-demethylation, lauric acid hydroxylase, and cinnamic acid 4-hydroxylase, were enhanced after pretreatment of cells with 2,4-D, procloraz, mecoprop, chlorotoluron, and oxime ether safeners. Effects of various agrochemicals were also determined on chlorotoluron ring-methyl hydroxylase and N-demethylase, following their direct addition to microsomal preparations. Plant growth regulators and fungicides, as well as piperonyl butoxide decreased both activities, tetcyclacis, and procloraz being markedly inhibitory. Naphthalic anhydride, oxime ether safeners, dichlormid, and tridiphane had only weak effects. The substrate specificities of chlorotoluron ring-methyl hydroxylase and N-demethylase were also investigated using structural analogues of the herbicide. Diuron was the strongest inhibitor among the tested phenylureas. Other herbicides that can be metabolized by wheat affected both activities to different extents. However, diclofop enhanced only chlorotoluron N-demethylase.