Phenylalanine aminomutase that catalyzes the rearrangement of L-phenylalanine to R-beta-phenylalanine. Catalyzes the first committed step in the biosynthesis of the side chain of the alkaloid taxol (paclitaxel), a widely-used compound with antitumor activity. Has also low phenylalanine ammonia-lyase activity and can catalyze the amination of trans-cinnamate. L-phenylalanine = L-beta-phenylalanine L-phenylalanine = (E)-cinnamate + NH4(+) Optimum pH is 7.5-8.0. Alkaloid biosynthesis; taxol biosynthesis. Phenylpropanoid metabolism; trans-cinnamate biosynthesis; trans-cinnamate from L-phenylalanine: step 1/1. Homodimer (PubMed:15878763). Homotetramer, dimer of dimers (PubMed:24786474). Contains an active site 4-methylidene-imidazol-5-one (MIO), which is formed autocatalytically by cyclization and dehydration of residues Ala-Ser-Gly. Could be used for the stereoselective biosynthesis of beta-amino acids via amination of cinnamic acid derivatives. Belongs to the PAL/histidase family.