TIGR00118

acetolactate synthase, large subunit, biosynthetic type; Two groups of proteins form acetolactate from two molecules of pyruvate. The type of acetolactate synthase described in this model also catalyzes the formation of acetohydroxybutyrate from pyruvate and 2-oxobutyrate, an early step in the branched chain amino acid biosynthesis; it is therefore also termed acetohydroxyacid synthase. In bacteria, this catalytic chain is associated with a smaller regulatory chain in an alpha2/beta2 heterotetramer. Acetolactate synthase is a thiamine pyrophosphate enzyme. In this type, FAD and Mg++ are also found. Several isozymes of this enzyme are found in E. coli K12, one of which contains a frameshift in the large subunit gene and is not expressed [Amino acid biosynthesis, Pyruvate family].