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. Also has low phenylalanine ammonia-lyase activity. L-phenylalanine = L-beta-phenylalanine L-phenylalanine = (E)-cinnamate + NH4(+) kcat is 0.053 sec(-1) for L-phenylalanine. Alkaloid biosynthesis; taxol biosynthesis. Phenylpropanoid metabolism; trans-cinnamate biosynthesis; trans-cinnamate from L-phenylalanine: step 1/1. Homotetramer. Contains an active site 4-methylidene-imidazol-5-one (MIO), which is formed autocatalytically by cyclization and dehydration of residues Ala-Ser-Gly. Belongs to the PAL/histidase family.