Catalyzes the non-oxidative deamination of L-phenylalanine to form trans-cinnamic acid and a free ammonium ion (PubMed:31655558). 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 higher in fruiting bodies and spores than in primordia, and very low in mycelia (PubMed:31655558). In the fruiting body, present in the cap, gill, pileipellis but not in the stipe (PubMed:31655558). Induced by thermal stress. Contains an active site 4-methylidene-imidazol-5-one (MIO), which is formed autocatalytically by cyclization and dehydration of residues Ala-Ser-Gly. RNAi-mediated knockdown results in delayed primordium formation. Belongs to the PAL/histidase family.