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Alcohol dehydrogenase activity varies between men and women, between young and old, and among populations from different areas of the world. For example, young women are unable to process alcohol at the same rate as young men because they do not express the alcohol dehydrogenase as highly, although the inverse is true among the middle-aged. [37]
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]
The reinforcing effects of alcohol consumption are mediated by acetaldehyde generated by catalase and other oxidizing enzymes such as cytochrome P-4502E1 in the brain. [60] Although acetaldehyde has been associated with some of the adverse and toxic effects of ethanol, it appears to play a central role in the activation of the mesolimbic ...
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 .
Metabolites involved in the kynurenine pathway include tryptophan, kynurenine, kynurenic acid, xanthurenic acid, quinolinic acid, and 3-hydroxykynurenine. [2] [3] The kynurenine pathway is responsible for about 95% of total tryptophan catabolism. [4] Disruption in the pathway is associated with certain genetic and psychiatric disorders. [5] [2 ...
Expression of tryptophan 2,3-dioxygenase in mammals is normally restricted to the liver, but it has been identified in the brain and epididymis of some species, and, in some tissues, its production can be induced in response to stimuli. [8] TDO from rat was the first to be expressed recombinantly (in E. coli). [10] Human TDO has also been ...
The pathway for the synthesis of serotonin from tryptophan. In animals and humans, serotonin is synthesized from the amino acid L-tryptophan by a short metabolic pathway consisting of two enzymes, tryptophan hydroxylase (TPH) and aromatic amino acid decarboxylase (DDC), and the coenzyme pyridoxal phosphate. The TPH-mediated reaction is the rate ...
The enzyme is highly specific, not accepting indole derivatives - which is unusual as many other enzymes involved in the production of catecholamines do. Tryptophan is a poor substrate for tyrosine hydroxylase, however it can hydroxylate L -phenylalanine to form L -tyrosine and small amounts of 3-hydroxyphenylalanine.