Catalyzes the first reaction in the catabolism of the essential branched chain amino acids leucine, isoleucine, and valine. Catalyzes the formation of methionine from 2-keto-4-methylthiobutyrate (KMTB) in the methionine salvage pathway primarily using branched chain amino acids (leucine, isoleucine, and valine) as well as lysine and proline as the amino donors. Involved in cell cycle regulation. 2-oxoglutarate + L-leucine = 4-methyl-2-oxopentanoate + L-glutamate 2-oxoglutarate + L-isoleucine = (S)-3-methyl-2-oxopentanoate + L-glutamate 2-oxoglutarate + L-valine = 3-methyl-2-oxobutanoate + L-glutamate Amino-acid biosynthesis; L-isoleucine biosynthesis; L-isoleucine from 2-oxobutanoate: step 4/4. Amino-acid biosynthesis; L-leucine biosynthesis; L-leucine from 3-methyl-2-oxobutanoate: step 4/4. Amino-acid biosynthesis; L-valine biosynthesis; L-valine from pyruvate: step 4/4. Amino-acid biosynthesis; L-methionine biosynthesis via salvage pathway; L-methionine from S-methyl-5-thio-alpha-D-ribose 1-phosphate: step 6/6. Highly expressed during stationary phase, down-regulated during logarithmic phase of growth. Down-regulated in the presence of repressive nitrogen sources (glutamine) and derepressed in secondary non-repressive nitrogen sources such as GABA. Highly expressed on cultures with isoleucine, leucine and valine as sole nitrogen source (catabolic conditions). Present with 25900 molecules/cell in log phase SD medium. Belongs to the class-IV pyridoxal-phosphate-dependent aminotransferase family. Extended N-terminus.