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Phenylalanine hydroxylase (PAH) (EC 1.14.16.1) is an enzyme that catalyzes the hydroxylation of the aromatic side-chain of phenylalanine to generate tyrosine.PAH is one of three members of the biopterin-dependent aromatic amino acid hydroxylases, a class of monooxygenase that uses tetrahydrobiopterin (BH 4, a pteridine cofactor) and a non-heme iron for catalysis.
The enzyme phenylalanine hydroxylase normally converts the amino acid phenylalanine into the amino acid tyrosine. If this reaction does not take place, phenylalanine accumulates and tyrosine is deficient. Excessive phenylalanine can be metabolized into phenylketones through the minor route, a transaminase pathway with glutamate.
Phenylalanine (symbol Phe or F) [3] ... (PKU) is the inability to metabolize phenylalanine because of a lack of the enzyme phenylalanine hydroxylase. Individuals with ...
These infants exhibit normal phenylalanine hydroxylase (PAH) enzymatic activity but have a deficiency in dihydropteridine reductase (DHPR), an enzyme required for the regeneration of tetrahydrobiopterin (THB or BH 4), a cofactor of PAH. [citation needed] Less frequently, DHPR activity is normal but a defect in the biosynthesis of THB exists. In ...
Phenylalanine is an amino acid obtained normally through the diet, but can be harmful if excess levels build up, causing intellectual disability and other serious health problems. In healthy individuals, it is metabolised ( hydroxylated ) into tyrosine , another amino acid, by phenylalanine hydroxylase .
Phenylalanine hydroxylase catalyzes the conversion of L-phenylalanine to L-tyrosine. Tyrosine hydroxylase catalyzes the rate-limiting step in catecholamine biosynthesis: the conversion of L-tyrosine to L-DOPA. Similarly, tryptophan hydroxylase catalyzes the rate-limiting step in serotonin biosynthesis: the conversion of L-tryptophan to 5 ...
4-Hydroxyphenylpyruvic acid (4-HPPA) is an intermediate in the metabolism of the amino acid phenylalanine. The aromatic side chain of phenylalanine is hydroxylated by the enzyme phenylalanine hydroxylase to form tyrosine. The conversion from tyrosine to 4-HPPA is in turn catalyzed by tyrosine aminotransferase. [2]
Tetrahydrobiopterin (BH 4, THB), also known as sapropterin (INN), [5] [6] is a cofactor of the three aromatic amino acid hydroxylase enzymes, [7] used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin (5-hydroxytryptamine, 5-HT), melatonin, dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), and is a cofactor for the ...
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