Q8IWU9

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the biosynthesis of serotoninby converting tryptophan to 5-hydroxy-L-tryptophan. Two isoforms of TPH exist: TPH-1 is mainly expressed in the periphery, whereas the expression of TPH-2 is restricted to neuronal cells and the central nervous system. TPH2 is a member of the pterin-dependent aromatic acid hydroxylase family. TPH2 protein catalyzes the first and rate limiting step in the biosynthesis of serotonin, an important hormone and neurotransmitter. Mutations in this gene may be associated with psychiatric diseases such as bipolar affective disorder and major depression.