Amino Acids

, Volume 41, Issue 5, pp 1195–1205 | Cite as

Tryptophan metabolism, from nutrition to potential therapeutic applications

  • Nathalie Le Floc’h
  • Winfried Otten
  • Elodie Merlot
Invited Review


Tryptophan is an indispensable amino acid that should to be supplied by dietary protein. Apart from its incorporation into body proteins, tryptophan is the precursor for serotonin, an important neuromediator, and for kynurenine, an intermediary metabolite of a complex metabolic pathway ending with niacin, CO2, and kynurenic and xanthurenic acids. Tryptophan metabolism within different tissues is associated with numerous physiological functions. The liver regulates tryptophan homeostasis through degrading tryptophan in excess. Tryptophan degradation into kynurenine by immune cells plays a crucial role in the regulation of immune response during infections, inflammations and pregnancy. Serotonin is synthesized from tryptophan in the gut and also in the brain, where tryptophan availability is known to influence the sensitivity to mood disorders. In the present review, we discuss the major functions of tryptophan and its role in the regulation of growth, mood, behavior and immune responses with regard to the low availability of this amino acid and the competition between tissues and metabolic pathways for tryptophan utilization.


Tryptophan Metabolism Nutrition Immune response Mood disorders 


Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Nathalie Le Floc’h
    • 1
    • 2
  • Winfried Otten
    • 3
  • Elodie Merlot
    • 1
    • 2
  1. 1.INRA, UMR1079, Système d’ElevageNutrition Animale et Humaine (SENAH)Saint GillesFrance
  2. 2.Agrocampus OuestUMR1079 SENAHRennesFrance
  3. 3.Research Unit Behavioural PhysiologyLeibniz Institute for Farm Animal BiologyDummerstorfGermany

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