| Description | Phenylalanine, tyrosine and tryptophan hydroxylases constitute a family of tetrahydrobiopterin-dependent aromatic amino acid hydroxylases, all of which are rate-limiting catalysts for important metabolic pathways [ ]. The proteins are structurally and functionally related, each containing iron, and catalysing ring hydroxylation of aromatic amino acids, using tetra-hydrobiopterin (BH4) as a substrate. All are regulated by phosphorylation at serines in their N-termini. It has been suggested that the proteins each contain a conserved C-terminal catalytic (C) domain and an unrelated N-terminal regulatory (R) domain. It is possible that the R domains arose from genes that were recruited from different sources to combine with the common gene for the catalytic core. Thus, by combining with the same C domain, the proteins acquired the unique regulatory properties of the separate R domains.A variety of enzymes belong to this family that includes, phenylalanine-4-hydroxylase from Chromobacterium violaceum where it is copper-dependent; it is iron-dependent in Pseudomonas aeruginosa, phenylalanine-4-hydroxylase catalyzes the conversion of phenylalanine to tyrosine. In humans, deficiencies are the cause of phenylketonuria, the most common inborn error of amino acid metabolism [ ], tryptophan 5-hydroxylase catalyzes the rate-limiting step in serotonin biosynthesis: the conversion of tryptophan to 3-hydroxy-anthranilate and tyrosine 3-hydroxylase catalyzes the rate limiting step in catecholamine biosynthesis: the conversion of tyrosine to 3,4-dihydroxy-L-phenylalanine.Enzymes that belong to this family are functionally as well as structurally related [ ]. Their size ranges from 260 residues for bacterial PAH, to about 500 residues for eukaryotic PAH, TYH and TRH. The signature pattern used in this entry is to a conserved region in the central part of these enzymes, which contains two conserved histidines that are involved in the binding to iron or copper []. | Name | Aromatic amino acid hydroxylase, iron/copper binding site |
| Short Name | ArAA_hydroxylase_Fe/CU_BS | Type | Binding_site |
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