IUBMB Enzyme Nomenclature


Accepted name: indoleamine 2,3-dioxygenase

Reaction: (1) D-tryptophan + O2 = N-formyl-D-kynurenine
(2) L-tryptophan + O2 = N-formyl-L-kynurenine

For diagram, click here

Other name(s): IDO (ambiguous); tryptophan pyrrolase (ambiguous); D-tryptophan:oxygen 2,3-oxidoreductase (decyclizing)

Systematic name: D-tryptophan:oxygen 2,3-oxidoreductase (ring-opening)

Comments: A protohemoprotein. Requires ascorbic acid and methylene blue for activity. This enzyme has broader substrate specificity than EC, tryptophan 2,3-dioxygenase [1]. It is induced in response to pathological conditions and host-defense mechanisms and its distribution in mammals is not confined to the liver [2]. While the enzyme is more active with D-tryptophan than L-tryptophan, its only known function to date is in the metabolism of L-tryptophan [2,6]. Superoxide radicals can replace O2 as oxygen donor [4,7].

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9014-51-1


1. Yamamoto, S. and Hayaishi, O. Tryptophan pyrrolase of rabbit intestine. D- and L-tryptophan-cleaving enzyme or enzymes. J. Biol. Chem. 242 (1967) 5260-5266. [PMID: 6065097]

2. Yasui, H., Takai, K., Yoshida, R. and Hayaishi, O. Interferon enhances tryptophan metabolism by inducing pulmonary indoleamine 2,3-dioxygenase: its possible occurrence in cancer patients. Proc. Natl. Acad. Sci. USA 83 (1986) 6622-6626. [PMID: 2428037]

3. Takikawa, O., Yoshida, R., Kido, R. and Hayaishi, O. Tryptophan degradation in mice initiated by indoleamine 2,3-dioxygenase. J. Biol. Chem. 261 (1986) 3648-3653. [PMID: 2419335]

4. Hirata, F., Ohnishi, T. and Hayaishi, O. Indoleamine 2,3-dioxygenase. Characterization and properties of enzyme. O2- complex. J. Biol. Chem. 252 (1977) 4637-4642. [PMID: 194886]

5. Dang, Y., Dale, W.E. and Brown, O.R. Comparative effects of oxygen on indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase of the kynurenine pathway. Free Radic. Biol. Med. 28 (2000) 615-624. [PMID: 10719243]

6. Littlejohn, T.K., Takikawa, O., Truscott, R.J. and Walker, M.J. Asp274 and His346 are essential for heme binding and catalytic function of human indoleamine 2,3-dioxygenase. J. Biol. Chem. 278 (2003) 29525-29531. [PMID: 12766158]

7. Thomas, S.R. and Stocker, R. Redox reactions related to indoleamine 2,3-dioxygenase and tryptophan metabolism along the kynurenine pathway. Redox Rep. 4 (1999) 199-220. [PMID: 10731095]

8. Sono, M. Spectroscopic and equilibrium studies of ligand and organic substrate binding to indolamine 2,3-dioxygenase. Biochemistry 29 (1990) 1451-1460. [PMID: 2334706]

[EC created 2006]

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