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A man with pellagra, which is caused by a chronic lack of vitamin B 3 in the diet. Severe deficiency of niacin in the diet causes the disease pellagra, characterized by diarrhea, sun-sensitive dermatitis involving hyperpigmentation and thickening of the skin (see image), inflammation of the mouth and tongue, delirium, dementia, and if left untreated, death. [7]
Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic beta carbon substituent. Tryptophan is also a precursor to the neurotransmitter serotonin, the hormone melatonin, and vitamin B 3 (niacin). [4] It is encoded by the codon UGG.
[1] [2] The amino acids L-tryptophan and L-5-hydroxytryptophan (5-HTP; oxitriptan) are precursors of serotonin and melatonin, while the amino acids L-phenylalanine, L-tyrosine, and L-DOPA (levodopa) are precursors of dopamine, epinephrine (adrenaline), and norepinephrine (noradrenaline).
Example of a label showing the amount of niacin (Vitamin B3), and specifying to be niacinamide in the ingredient section.. The United States adopted in 1942 the terms niacin to nicotinic acid and niacinamide to nicotinamide to avoid references to nicotine, [12] [13] the terms were incorporated into the United States Adopted Name [14] that was created later in 1961.
Phenylalanine, tyrosine, and tryptophan, the aromatic amino acids, arise from chorismate. The first step, condensation of 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) from PEP/E4P, uses three isoenzymes AroF, AroG, and AroH. Each one of these has its synthesis regulated from tyrosine, phenylalanine, and tryptophan, respectively.
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 ...
Synthesis of B 3 from tryptophan involves vitamin B 2 and B 6, so deficiencies in either of these nutrients can lead to niacin deficiency. An excess of leucine, an essential amino acid, in the diet can also interfere with tryptophan conversion and subsequently result in a B 3 deficiency. [114]
Tyr behaves similarly to phenylalanine (precursor to tyrosine) and tryptophan, and is a precursor of melanin, epinephrine, and thyroid hormones. Naturally fluorescent, its fluorescence is usually quenched by energy transfer to tryptophans. Glutamic acid or glutamine: Z Glx A placeholder when either amino acid may occupy a position