The Uniqueness of Tryptophan in Biology: Properties, …
The serotonin pathway is initiated by tryptophan hydroxylase (TPH) that adds a hydroxy group to the 5 position of Trp to generate 5-HTP, also called oxitriptan. The kynurenine pathway is initiated by either of the two heme-containing oxidoreductases, indoleamine 2,3-dioxygenase (IDO) or the highly related tryptophan 2,3-dioxygenase …