Biopterin-dependent aromatic amino acid hydroxylase; a family of non-heme, iron(II)-dependent enzymes that includes prokaryotic and eukaryotic phenylalanine-4-hydroxylase (PheOH), eukaryotic tyrosine hydroxylase (TyrOH) and eukaryotic tryptophan hydroxylase (TrpOH). PheOH converts L-phenylalanine to L-tyrosine, an important step in phenylalanine catabolism and neurotransmitter biosynthesis, and is linked to a severe variant of phenylketonuria in humans. TyrOH and TrpOH are involved in the biosynthesis of catecholamine and serotonin, respectively. The eukaryotic enzymes are all homotetramers.
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