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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.
Niacin deficiency is a consequence of a diet low in both niacin and the amino acid tryptophan, a precursor for the vitamin. Low plasma tryptophan is a non-specific indicator, meaning it can have other causes. The signs and symptoms of niacin deficiency start to revert within days of oral supplementation with large amounts of the vitamin. [23] [24]
Carcinoid syndrome thus may produce niacin deficiency and clinical manifestations of pellagra. Anti-tuberculosis medication tends to bind to vitamin B 6 and reduce niacin synthesis, since B 6 (pyridoxine) is a required cofactor in the tryptophan-to-niacin reaction. Several therapeutic drugs can provoke pellagra.
Hartnup disease (also known as "pellagra-like dermatosis" [1] and "Hartnup disorder" [2]) is an autosomal recessive [3] metabolic disorder affecting the absorption of nonpolar amino acids (particularly tryptophan that can be, in turn, converted into serotonin, melatonin, and niacin).
However, the human body can produce NAD + from the amino acid tryptophan and niacin without our ingestion of nicotinamide. [33] NAD + acts as an electron carrier that mediates the interconversion of energy between nutrients and the cell's energy currency, adenosine triphosphate (ATP). In oxidation-reduction reactions, the active part of the ...
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In organisms, NAD can be synthesized from simple building-blocks from either tryptophan or aspartic acid, each a case of an amino acid. Alternatively, more complex components of the coenzymes are taken up from nutritive compounds such as niacin ; similar compounds are produced by reactions that break down the structure of NAD, providing a ...