Inhibition of the biosynthesis of fatty acids is an important mode of action for a variety of postemergence herbicides.  These include the aryloxypropionic acid derivatives and substituted cyclohexanediones, used to control annual and perennial grasses.  In grasses these herbicides block fatty acid biosynthesis by inhibiting the transcarboxylation step in the transformation of acetyl Co-A into malonyl Co-A by the enzyme acetyl Co-A carboxylase.  Broadleaf crop plants  in weed-treated fields are not affected.  Two enzymatic steps are involved:  1) the carboxylation of biotin linked to a carrier protein and 2) the transfer of this biotin activated carboxyl group to acetyl Co-A.  Although the transcarboxylation domain is the binding region, both classes of herbicides interact with different sets of residues in the protein and bind at slightly different, overlapping zones.  In this study, binding by congeners of these herbicide classes was modeling by molecular docking of these herbicide molecules with carboxylase and compared with known structures.  Binding affinities in the protein were computed and compared for aryloxypropionic acids and cyclohexanediones using ab initio and density functional methods.

Modeling of herbicide binding in the inhibition of acetyl-CoA carboxylase

244th National Meeting (2012)

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