RING-METHYL HYDROXYLATION OF CHLORTOLURON BY AN INDUCIBLE CYTOCHROME P450-DEPENDENT ENZYME FROM MAIZE

Article abstract of DOI:10.1016/0031-9422(90)87077-8

An enzyme catalysing ring-methyl hydroxylation of the substituted phenylurea herbicide chlortoluron was detected in isolated microsomes from germinating maize.Chlortoluron hydroxylation was absolutely dependent on NADPH and molecular oxygen.The enzyme was inhibited by carbon monoxide in the presence of oxygen and this inhibition could be reversed by light.Several known inhibitors of cytochrome P450 enzymes inhibited chlortoluron hydroxylation to varying degrees.It is concluded that the newly detected enzyme is a cytochrome P450-dependent mixed function oxidase.Enzyme activity was stimulated 15-fold by treatment of maize seeds with the herbicide antidote CGA 154281 <4-(dichloroacetyl)-3,4-dihydro-3-methyl-2H-1,4-benzoxazine>.