Cyclohexanedione Herbicides Are Selective and Potent Inhibitors of Acetyl-CoA Carboxylase from Grasses

Biochemical studies of plant species susceptible to the cyclohexanedione herbicides, alloxydim, sethoxydim, and clethodim, have demonstrated that these selective grass herbicides inhibit acetyl-coenzyme A carboxylase, the second enzyme common to both fatty acid and flavonoid biosynthetic pathways. The K i s for the cyclohexanediones tested ranged from 0.02 to 1.95 micromolar, depending on the species. The enzyme isolated from broadleaf plants was much less sensitive to inhibition by these herbicides (K i s from 53 micromolar to 2.2 millimolar). These results may explain the mechanism of action of these herbicides and their selectivity for monocotyledonous species.