BAT1 and BAT2 respectively encode the mitochondrial and cytosolic branched-chain amino acid aminotransferases (BCAATases) (1). BCAATases are required for both branched-chain amino acid biosynthesis and Ehrlich pathway amino acid catabolism; Bat1p and Bat2p catalyze the transfer of amino groups between the amino acids valine, isoleucine, and leucine and their corresponding alpha-keto-acids. Alpha-keto-acids are biosynthetic precursors of fusel alcohols, which influence the aroma and flavor of yeast-derived fermentation products such as beer and bread (6 and references contained therein).

Bat1p and Bat2p are 77% identical to each other and orthologs have been identified in S. pombe, worm, mouse, and human (1, 7). BAT1 is highly expressed during logarithmic phase and repressed during stationary phase, while BAT2 is expressed during stationary phase and repressed during logarithmic growth (3). On glucose-containing media, single deletion of either BAT gene impairs neither cell growth nor fusel alcohol production, but deletion of both genes results in branched-chain amino acid auxotrophy and severe growth retardation (1).

Last updated: 2007-04-30