Tryptophan metabolism

Tryptophan metabolism refers to a **complex network of biochemical pathways** responsible for the breakdown and utilization of tryptophan, an essential amino acid. It is not a single molecule or receptor but encompasses several distinct enzymatic routes: 1. **Kynurenine Pathway:** The primary route in mammals, catalyzed by tryptophan 2,3-dioxygenase (TDO) in the liver and indoleamine 2,3-dioxygenase (IDO) extrahepatically. This leads to production of neuroactive metabolites such as kynurenic acid and quinolinic acid. Dysregulation is implicated in cancer immune escape and neurodegeneration[1][4][5]. 2. **Serotonin Pathway:** In serotonergic neurons and some peripheral tissues, tryptophan is converted by tryptophan hydroxylase into serotonin—a key neurotransmitter—and further into melatonin via N-acetylserotonin[1][7]. 3. **Indole Pathways:** In gut microbiota, tryptophan can be metabolized into indoles that modulate host immunity through receptors like aryl hydrocarbon receptor; these microbial products influence mucosal homeostasis and inflammation[1][4]. Because "tryptophan metabolism" describes a set of interconnected pathways rather than a discrete molecular target such as an enzyme or receptor, it does *not* fit standard definitions used for therapeutic targets like "receptor," "enzyme," or "transporter." Instead, individual enzymes within these pathways—such as IDO1/IDO2/TDO—are considered drug targets due to their roles in disease processes including cancer immunosuppression and chronic inflammation[5]. Drugs have been developed against these specific enzymes rather than against “tryptophan metabolism” as a whole. Therefore: > The entry “Tryptophan metabolism” is not itself a canonical therapeutic target but rather describes multiple biological processes involving many potential druggable proteins. If you are seeking structured information on actionable targets within this system—for example “indoleamine 2,3-dioxygenase 1”—those should be specified individually. **Summary judgment:** “Tryptophan metabolism” is too broad/vague to serve directly as a canonical molecular target; it should be replaced with more precise entries corresponding to its constituent enzymes or receptors involved in disease-relevant biology.[1][4][5]

Other names

Tryptophan metabolic pathwayTrp metabolismTRP pathwayKynurenine pathway (sub-pathway)Serotonin pathway (sub-pathway)Indole pathway (sub-pathway)