Converts 2-oxo acids to branched-chain amino acids (BCAA). Shows no kinetic preferences corresponding to anabolic or catabolic functions, but likely involved in BCAA catabolism. 2-oxoglutarate + L-isoleucine = (S)-3-methyl-2-oxopentanoate + L-glutamate 2-oxoglutarate + L-leucine = 4-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. Expressed specifically in lupulin glands. 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.