Catalyzes the non-oxidative deamination of L-phenylalanine to form trans-cinnamic acid and a free ammonium ion (By similarity). Facilitates the commitment step in phenylpropanoid pathways that produce secondary metabolites such as lignins, coumarins and flavonoids (By similarity). L-phenylalanine = (E)-cinnamate + NH4(+) Phenylpropanoid metabolism; trans-cinnamate biosynthesis; trans-cinnamate from L-phenylalanine: step 1/1. Homotetramer. Expression is the highest in mycelia, and decreases during fruiting body development (PubMed:26539050). In the fruiting body, present in the stipe but not in the pileus (PubMed:26539050). Induced when grown in presence of ammonium nitrate, L-phenylalanine, L-tryptophan and L-tyrosine. 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.