Tryptophan 5-hydroxylase 1 (TPH1)

Tryptophan 5-hydroxylase 1 (TPH1) is an isoenzyme of tryptophan hydroxylase, encoded by the *TPH1* gene. It catalyzes the rate-limiting step in serotonin biosynthesis by converting L-tryptophan to 5-hydroxy-L-tryptophan (5-HTP), which is then decarboxylated to form serotonin. TPH1 is primarily expressed in peripheral tissues. It plays key roles as a neurotransmitter/hormone involved in gut motility, vascular tone regulation, platelet aggregation, and immune modulation. Recent research highlights immunoregulatory functions and suggests that tryptophan depletion itself has immunomodulatory consequences. Pharmacological inhibition of tryptophan hydroxylases can reduce peripheral serotonin synthesis; conversely, increased substrate availability may have antidepressant effects.

Other names

TPRHTRPHtryptophan hydroxylase 1

Inhibition of tryptophan hydroxylase to reduce peripheral serotonin synthesis; Modulation of serotonin production through substrate availability.