articleNutrientsFeb 2, 2026GOLD OA

Serotonin, Kynurenine, and Indole Pathways of Tryptophan Metabolism in Humans in Health and Disease

Charles University · University of Hradec Králové

PubMed
Indexed incrossrefpubmed

Abstract

Tryptophan (TRP) is a proteinogenic and nutritionally essential amino acid involved in the formation of numerous bioactive substances. A crucial role in the TRP molecule is played by indole, a bicyclic ring formed by benzene and pyrrole, which confers hydrophobic and antioxidant properties and the ability to act as a ligand for aryl hydrocarbon and pregnane X receptors. The first parts of the article examine sources, nutritional requirements, and three pathways of TRP catabolism. Physiologically, ~5% of dietary TRP is catabolized through the pathway forming serotonin and melatonin in the brain and enterochromaffin cells of the gut, ~85% through the pathway resulting in the formation of nicotinamide nucleotides…

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4
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47.72
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99%
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246
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Authors

1

Topics & keywords

Keywords
  • Kynurenine pathway
  • Aryl hydrocarbon receptor
  • Catabolism
  • Melatonin
  • Tryptophan
  • Kynurenine
  • Metabolic pathway
  • Indole test
UN Sustainable Development Goals
  • Zero hunger
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