Bacterial acetohydroxyacid synthase and its inhibitors--a summary of their structure, biological activity and current status.

Acetohydroxyacid synthase (anabolic AHAS; EC 2.2.1.6) is a thiamin diphosphate-dependent enzyme that catalyzes the first step in the branched-chain amino acid (BCAA) biosynthesis pathway. BCAAs are synthesized by plants, algae, fungi and bacteria, although not by animals. Thus, the enzymes of the BCAA biosynthetic pathway are potential targets in the development of herbicides, fungicides and antimicrobial compounds. Plant AHASs are well studied in this regard because specific plant AHAS inhibitors are considered to comprise the most potent herbicides. These inhibitors are also effective against bacterial AHASs, inhibit the growth of several bacterial strains and have little to no toxicity in mammals. This review provides an overview of bacterial AHASs with an update of the current status of AHAS inhibitors.