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 degradation; L-leucine degradation; 4-methyl-2-oxopentanoate from L-leucine (aminotransferase route): step 1/1. Amino-acid degradation; L-valine degradation. 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.