Broad-specificity enzyme that catalyzes the transamination of 2-ketoisocaproate, p-hydroxyphenylpyruvate, and phenylpyruvate to yield leucine, tyrosine, and phenylalanine, respectively. In vitro, is able to catalyze the conversion of beta-methyl phenylpyruvate to the nonproteinogenic amino acid (2S,3S)-beta-methyl-phenylalanine, a building block of the antibiotic mannopeptimycin produced by Streptomyces hygroscopicus NRRL3085. 2-oxoglutarate + an aromatic L-alpha-amino acid = an aromatic oxo-acid + L-glutamate (2S,3S)-3-methylphenylalanine + 2-oxoglutarate = (3S)-2-oxo-3-phenylbutanoate + L-glutamate Amino-acid biosynthesis; L-phenylalanine biosynthesis; L-phenylalanine from phenylpyruvate (ArAT route): step 1/1. Amino-acid biosynthesis; L-tyrosine biosynthesis; L-tyrosine from (4-hydroxyphenyl)pyruvate: step 1/1. Homodimer. Belongs to the class-I pyridoxal-phosphate-dependent aminotransferase family.