Indoleamine 2,3-dioxygenase

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Indoleamine 2,3-dioxygenase 1
PBB Protein INDO image.jpg
PDB rendering based on 2d0t.
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols IDO1 ; IDO; IDO-1; INDO
External IDs OMIM147435 MGI96416 HomoloGene48082 ChEMBL: 4685 GeneCards: IDO1 Gene
EC number
RNA expression pattern
PBB GE INDO 210029 at tn.png
More reference expression data
Species Human Mouse
Entrez 3620 15930
Ensembl ENSG00000131203 ENSMUSG00000031551
UniProt P14902 P28776
RefSeq (mRNA) NM_002164 NM_001293690
RefSeq (protein) NP_002155 NP_001280619
Location (UCSC) Chr 8:
39.76 – 39.79 Mb
Chr 8:
24.58 – 24.6 Mb
PubMed search [1] [2]

Indoleamine-pyrrole 2,3-dioxygenase (IDO or INDO EC is an enzyme that in humans is encoded by the IDO1 gene.[1][2] This enzyme catalyzes the degradation of the essential amino acid L-tryptophan to N-formylkynurenine.[3]


Indoleamine 2,3-dioxygenase is the first and rate-limiting enzyme of tryptophan catabolism through kynurenine pathway, thus causing depletion of tryptophan which can cause halted growth of microbes as well as T cells.

IDO is an immunomodulatory enzyme produced by some alternatively activated macrophages and other immunoregulatory cells (also used as an immune subversion strategy by many tumors). Interferon-gamma has an antiproliferative effect on many tumor cells and inhibits intracellular pathogens such as Toxoplasma and chlamydia, at least partly because of the induction of indoleamine 2,3-dioxygenase.

It has been shown that IDO permits tumor cells to escape the immune system by depletion of L-Trp in the microenvironment of cells. Indeed, wide range of human cancers such as prostatic, colorectal, pancreatic, cervical, gastric, ovarian, head, lung, etc. overexpress human IDO (hIDO).[4]


Norharmane, via inhibition of indoleamine 2,3-dioxygenase exerts neuroprotective properties by suppressing kynurenine neurotoxic metabolites such as quinolinic acid, 3-hydroxy-kynurenine and nitric oxide synthase.[5] Rosmarinic acid inhibits the expression of indoleamine 2,3-dioxygenase via its cyclooxygenase-inhibiting properties.[6] COX-2 inhibitors down-regulate indoleamine 2,3-dioxygenase, leading to a reduction in kynurenine levels as well as reducing proinflammatory cytokine activity.[7] Alpha-Methyl-Tryptophan also inhibits indoleamine dioxygenase.[8]

Indoleamine 2,3-dioxygenase
PDB 2d0t EBI.jpg
crystal structure of 4-phenylimidazole bound form of human indoleamine 2,3-dioxygenase
Symbol IDO
Pfam PF01231
Pfam clan CL0380
InterPro IPR000898
Indoleamine 2,3-dioxygenase
EC number
CAS number 9014-51-1
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

See also[edit]


Tryptophan 2,3-dioxygenase


  1. ^ Dai W, Gupta SL (April 1990). "Molecular cloning, sequencing and expression of human interferon-gamma-inducible indoleamine 2,3-dioxygenase cDNA". Biochem. Biophys. Res. Commun. 168 (1): 1–8. doi:10.1016/0006-291X(90)91666-G. PMID 2109605. 
  2. ^ Najfeld V, Menninger J, Muhleman D, Comings DE, Gupta SL (1993). "Localization of indoleamine 2,3-dioxygenase gene (INDO) to chromosome 8p12-->p11 by fluorescent in situ hybridization". Cytogenet. Cell Genet. 64 (3–4): 231–2. doi:10.1159/000133584. PMID 8404046. 
  3. ^ "Entrez Gene: INDO indoleamine-pyrrole 2,3 dioxygenase". 
  4. ^ Uyttenhove,C.; Pilotte, L.; Théate, I.; Stroobant, V.; Colau, D.; Parmentier,N.; Boon, T.; Van den Eynde, B. J. Naturemedicine 2003,9, 1269-74
  5. ^ Chiarugi A, Dello Sbarba P, Paccagnini A, Donnini S, Filippi S, Moroni F (August 2000). "Combined inhibition of indoleamine 2,3-dioxygenase and nitric oxide synthase modulates neurotoxin release by interferon-gamma-activated macrophages". J. Leukoc. Biol. 68 (2): 260–6. PMID 10947071. 
  6. ^ Lee HJ, Jeong YI, Lee TH, et al. (May 2007). "Rosmarinic acid inhibits indoleamine 2,3-dioxygenase expression in murine dendritic cells". Biochem. Pharmacol. 73 (9): 1412–21. doi:10.1016/j.bcp.2006.12.018. PMID 17229401. 
  7. ^ Cesario A, Rocca B, Rutella S (2011). "The interplay between indoleamine 2,3-dioxygenase 1 (IDO1) and cyclooxygenase (COX)-2 in chronic inflammation and cancer". Curr. Med. Chem. 18 (15): 2263–71. doi:10.2174/092986711795656063. PMID 21517752. 
  8. ^

Further reading[edit]

External links[edit]