phenylalanine hydroxylase

Phenylalanine hydroxylase (PheOH, alternatively PheH or PAH) is an enzyme that catalyzes the hydroxylation of the aromatic side-chain of phenylalanine to generate tyrosine. PheOH is one of three members of the biopterin-dependent aromatic amino acid hydroxylases, a class of monooxygenase that uses tetrahydrobiopterin (BH₄, a pteridine cofactor) and a non-heme iron for catalysis. During the reaction, molecular oxygen is heterolytically cleaved with sequential incorporation of one oxygen atom into BH₄ and phenylalanine substrate.