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Tryptophan hydroxylase (TPH) is an enzyme (EC 1.14.16.4) involved in the synthesis of the monoamine neurotransmitter serotonin. Tyrosine hydroxylase , phenylalanine hydroxylase , and tryptophan hydroxylase together constitute the family of biopterin-dependent aromatic amino acid hydroxylases .
Because tryptophan is converted into 5-hydroxytryptophan (5-HTP) which is then converted into the neurotransmitter serotonin, it has been proposed that consumption of tryptophan or 5-HTP may improve depression symptoms by increasing the level of serotonin in the brain. Tryptophan is sold over the counter in the United States (after being banned ...
Tryptophan hydroxylase (TPH; EC 1.14.16.4) is the rate-limiting enzyme in the synthesis of serotonin (5-hydroxytryptamine, or 5HT). 5HT is causally involved in numerous central nervous activities, and it has several functions in peripheral tissues, including the maintenance of vascular tone and gut motility.[supplied by OMIM] [7]
5-HTP is produced from the amino acid tryptophan through the action of the enzyme tryptophan hydroxylase. Tryptophan hydroxylase is one of the biopterin-dependent aromatic amino acid hydroxylases. Production of 5-HTP is the rate-limiting step in 5-HT (serotonin) synthesis. 5-HTP is normally rapidly converted to 5-HT by amino acid decarboxylase. [1]
Tryptophan hydroxylases catalyze the biopterin-dependent monooxygenation of tryptophan to 5-hydroxytryptophan (5-HTP), which is subsequently decarboxylated by aromatic amino acid decarboxylase to form the neurotransmitter serotonin (5-hydroxytryptamine or 5-HT). It is the rate-limiting enzyme in the biosynthesis of serotonin.
L-Tryptophan to tryptamine – a trace amine neuromodulator; 5-HTP to serotonin (5-hydroxytryptamine) – a neurotransmitter; However, some of these reactions do not seem to bear much or any biological significance. For example, histamine is biosynthesised strictly via the enzyme histidine decarboxylase in humans and other organisms. [10] [11]
Serotonin and tryptophan have been found in chocolate with varying cocoa contents. The highest serotonin content (2.93 μg/g) was found in chocolate with 85% cocoa, and the highest tryptophan content (13.27–13.34 μg/g) was found in 70–85% cocoa. The intermediate in the synthesis from tryptophan to serotonin, 5-hydroxytryptophan, was not found.
Tetrahydrobiopterin has multiple roles in human biochemistry. The major one is to convert amino acids such as phenylalanine, tyrosine, and tryptophan to precursors of dopamine and serotonin, major monoamine neurotransmitters. [21] It works as a cofactor, being required for an enzyme's activity as a catalyst, mainly hydroxylases. [7]