Catalyzes the hydroxylation of L-phenylalanine (PubMed:18835579). Hydroxylates L-tryptophan to 5-hydroxy-L-tryptophan but does not hydroxylate L-tyrosine to L-DOPA (PubMed:18835579). It uses D-threo-tetrahydrodictyopterin (DH4), also known as dictyoperin, as a cofactor. (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin + L-phenylalanine + O2 = (4aS,6R)-4a-hydroxy-L-erythro-5,6,7,8-tetrahydrobiopterin + L-tyrosine (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin + L-tryptophan + O2 = (4aS,6R)-4a-hydroxy-L-erythro-5,6,7,8-tetrahydrobiopterin + 5-hydroxy-L-tryptophan Binds 1 Fe(2+) ion. Optimum temperature is 40 degrees Celsius. Amino-acid degradation; L-phenylalanine degradation; acetoacetate and fumarate from L-phenylalanine: step 1/6. Homotetramer. This enzyme uses tetrahydrodictyopterin (DH4), a D-threo isomer of biopterin, and not tetrahydrobiopterin (TH4) for it's catalytic activity. Belongs to the biopterin-dependent aromatic amino acid hydroxylase family.