Indoleamine 2,3-Dioxygenase (IDO)

Indoleamine 2,3-Dioxygenase (IDO) plays a crucial role in regulating immune cell function through the kynurenine pathway. It also depletes tryptophan in microenvironments, particularly in tumors, which has led to the development of IDO1 (indoleamine 2,3-dioxygenase1) inhibitors for cancer therapy. However, the connections between tryptophan depletion and product supply remain an ongoing challenge in cellular biochemistry and metabolism.
Fiore & Murray 2021 Current Opinion Immunology 70: 7-14

A tumoral immune resistance mechanism based on tryptophan degradation by indoleamine 2,3-dioxygenase (IDO).
Uyttenhove et al. 2003 Nature Med. 9: 1269-1274

T lymphocytes undergo proliferation arrest when exposed to tryptophan shortage, which can be provoked by IDO, an immune-modulating enzyme.
Uyttenhove et al. 2003 Nature Med. 9: 1269-1274

The enzyme indoleamine 2,3-dioxygenase (IDO) has a broad substrate specificity. It catalyzes the initial and rate-limiting step in the kynurenine pathway, which involves the oxidation of l-tryptophan to N-formylkynurenine. IDO can degrade various indoleamines, including l-Trp, d-Trp, serotonin, and melatonin. It also shows a wide recognition of substrates beyond l-tryptophan, such as many indole-containing compounds.
Sugimoto et al. 2006
Booth et al. 2015 THE JOURNAL OF BIOLOGICAL CHEMISTRY 290(52): 30924-30930

see also:
Cancer / Tumors & Kynurenine (Kyn)