tryptophan 2,3-dioxygenase | 1.13.11.- Dioxygenases | IUPHAR/BPS Guide to PHARMACOLOGY

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tryptophan 2,3-dioxygenase

target has curated data in GtoImmuPdb

Target id: 2887

Nomenclature: tryptophan 2,3-dioxygenase

Abbreviated Name: TDO2

Family: 1.13.11.- Dioxygenases

Annotation status:  image of a grey circle Awaiting annotation/under development. Please contact us if you can help with annotation.  » Email us

Gene and Protein Information
Species TM AA Chromosomal Location Gene Symbol Gene Name Reference
Human - 406 4q32.1 TDO2 tryptophan 2,3-dioxygenase
Mouse - 406 3 E3 Tdo2 tryptophan 2,3-dioxygenase
Rat - 406 2q33 Tdo2 tryptophan 2,3-dioxygenase
Previous and Unofficial Names
tryptophan peroxidase | tryptophan pyrrolase | tryptophanase | indolamine 2,3-dioxygenase | tryptamine 2,3-dioxygenase | TDO | TPH2 | tryptophan 2
Database Links
ChEMBL Target
Ensembl Gene
Entrez Gene
Human Protein Atlas
KEGG Enzyme
RefSeq Nucleotide
RefSeq Protein
Enzyme Reaction
EC Number:
Description Reaction Reference
Together with IDO1, catalyzes the first and rate-limiting step in the kynurenine pathway (major pathway of tryptophan metabolism). L-tryptophan + O2 <=> N-formyl-L-kynurenine

Download all structure-activity data for this target as a CSV file

Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Value Parameter Reference
LM10 Hs Inhibition 5.3 pKi 1,3
pKi 5.3 (Ki 5.6x10-6 M) [1,3]
LM10 Hs Inhibition 6.2 pIC50 3
pIC50 6.2 (IC50 6.2x10-7 M) [3]
Description: Concentration inhibiting TDO activity by 50% in a cellular assay, at 80μM L-tryptophan.
navoximod Hs Inhibition >6.0 pIC50 2
pIC50 >6.0 (IC50 <1x10-6 M) [2]
LM10 Mm Inhibition 5.7 pIC50 3
pIC50 5.7 (IC50 1.96x10-6 M) [3]
Description: Concentration inhibiting TDO activity by 50% in a cellular assay, at 80μM L-tryptophan.
View species-specific inhibitor tables
Inhibitor Comments
LM10 is >640-fold selective for TDO2 over IDO1 [3].
Immunopharmacology Comments
Depletion of tryptophan and metabolites promote Treg cell differentiation, suppression of immune response and decreased DC function. TDO2 inhibition reverses this [3].


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1. Dolusić E, Larrieu P, Moineaux L, Stroobant V, Pilotte L, Colau D, Pochet L, Van den Eynde B, Masereel B, Wouters J et al.. (2011) Tryptophan 2,3-dioxygenase (TDO) inhibitors. 3-(2-(pyridyl)ethenyl)indoles as potential anticancer immunomodulators. J. Med. Chem., 54 (15): 5320-34. [PMID:21726069]

2. Dounay AB, Tuttle JB, Verhoest PR. (2015) Challenges and Opportunities in the Discovery of New Therapeutics Targeting the Kynurenine Pathway. J. Med. Chem., 58 (22): 8762-82. [PMID:26207924]

3. Pilotte L, Larrieu P, Stroobant V, Colau D, Dolusic E, Frédérick R, De Plaen E, Uyttenhove C, Wouters J, Masereel B et al.. (2012) Reversal of tumoral immune resistance by inhibition of tryptophan 2,3-dioxygenase. Proc. Natl. Acad. Sci. U.S.A., 109 (7): 2497-502. [PMID:22308364]

How to cite this page

1.13.11.- Dioxygenases: tryptophan 2,3-dioxygenase. Last modified on 03/07/2019. Accessed on 10/07/2020. IUPHAR/BPS Guide to PHARMACOLOGY,