Center for Bioinformatics
Oxidoreductases | Transferases | Hydrolases | Lyases | Isomerases | Ligases

Basic Information

Enzyme Number

Official Name

tryptophan 2,3-dioxygenase

Name from literature

tryptophan 2,3-dioxygenase

Pathway from literature

kynurenine pathway/tryptophan catabolism

Pathway from KEGG

Amino Acid Metabolism; Tryptophan metabolism; map00380


Human (9606)

Genome localization

4q31-q32[6999 ],


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].

Rate-limiting Description

"The goal of this study was to determine the localization of Quin in unstimulated mice under conditions where rate-limiting control of the pathway by both TDO and IDO was by-passed." (10709788)

"Indoleamine 2,3-dioxgyenase (IDO) is a cytosolic heme protein which, together with the hepatic enzyme tryptophan 2,3-dioxygenase, catalyzes the first and rate-limiting step in the major pathway of tryptophan metabolism, the kynurenine pathway." (12766158)

"Liver L-tryptophan 2,3-dioxygenase activity (TDO), a rate-limiting enzyme of the kynurenine pathway, was increased in proportion to blood urea nitrogen and creatinine levels." (10966936)

Regulatory Information

Upstream transcription factor


Regulatory type


transcriptional factor;YY1(7528)

"Point mutations within 663-666 bp of intron 6 of the human TDO2 gene, associated with a number of psychiatric disorders, damage the YY-1 transcription factor binding site." (10580097)


"Quantitative phosphoproteome analysis using a dendrimer conjugation chemistry and tandem mass spectrometry." (16094384)

transcriptional level;

"The activity and mRNA expression level of indoleamine 2,3-dioxygenase in term placentas were significantly lower in preeclampsia. Could cause dysregulation of inflammatory response intrinsic to normal pregnancy." (12634647)





Gene ontology

Gene ontology

GO:0019674 (P) NAD metabolic process [P48775 ];
GO:0019441 (P) tryptophan catabolic process to kynurenine [P48775 ];
GO:0055114 (P) oxidation reduction [P48775 ];
GO:0005829 (C) cytosol [P48775 ];
GO:0005506 (F) iron ion binding [P48775 ];
GO:0004833 (F) tryptophan 2, 3-dioxygenase activity [P48775 ];




Entrez Gene




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  Last Modified: 2009-03-24  
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