IUBMB Enzyme Nomenclature


Accepted name: tryptophan 2,3-dioxygenase

Reaction: L-tryptophan + O2 = N-formyl-L-kynurenine

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Other name(s): tryptophan pyrrolase (ambiguous); tryptophanase; tryptophan oxygenase; tryptamine 2,3-dioxygenase; tryptophan peroxidase; indoleamine 2,3-dioxygenase (ambiguous); indolamine 2,3-dioxygenase (ambiguous); L-tryptophan pyrrolase; TDO; L-tryptophan 2,3-dioxygenase; L-tryptophan:oxygen 2,3-oxidoreductase (decyclizing)

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

Comments: A protohemoprotein. In mammals, the enzyme appears to be located only in the liver. This enzyme, together with EC, indoleamine 2,3-dioxygenase, catalyses the first and rate-limiting step in the kynurenine pathway, the major pathway of tryptophan metabolism [5]. The enzyme is specific for tryptophan as substrate, but is far more active with L-tryptophan than with D-tryptophan [2].

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


1. Uchida, K., Shimizu, T., Makino, R., Sakaguchi, K., Iizuka, T., Ishimura, Y., Nozawa, T. and Hatano, M. Magnetic and natural circular dichroism of L-tryptophan 2,3-dioxygenases and indoleamine 2,3-dioxygenase. I. Spectra of ferric and ferrous high spin forms. J. Biol. Chem. 258 (1983) 2519-2525. [PMID: 6600455]

2. Ren, S., Liu, H., Licad, E. and Correia, M.A. Expression of rat liver tryptophan 2,3-dioxygenase in Escherichia coli: structural and functional characterization of the purified enzyme. Arch. Biochem. Biophys. 333 (1996) 96-102. [PMID: 8806758]

3. Leeds, J.M., Brown, P.J., McGeehan, G.M., Brown, F.K. and Wiseman, J.S. Isotope effects and alternative substrate reactivities for tryptophan 2,3-dioxygenase. J. Biol. Chem. 268 (1993) 17781-17786. [PMID: 8349662]

4. 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]

5. 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]

[EC created 1961 as EC, deleted 1964, reinstated 1965 as EC, transferred 1972 to EC, modified 1989, modified 2006]

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