Converts 2-oxo acids to branched-chain amino acids. Acts on leucine, isoleucine and valine (By similarity). 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. A number of isoforms are produced. According to EST sequences. Branched-chain amino acids are synthesized in chloroplasts, whereas the degradation takes place in mitochondria. Belongs to the class-IV pyridoxal-phosphate-dependent aminotransferase family. The predicted gene has been split into 2 genes: At5g65780 and At5g65770.