Along with the enzymes encoded by the INDO (MIM 147435) and TDO2 (MIM 191070) genes, the enzyme encoded by the INDOL1 gene metabolizes tryptophan in the kynurenine pathway (Ball et al., 2007 [PubMed 17499941]).[supplied by OMIM, Feb 2011] See more...

Aliases for IDO2 Gene

Aliases for IDO2 Gene

  • Indoleamine 2,3-Dioxygenase 2 2 3 4 5
  • Indoleamine-Pyrrole 2,3-Dioxygenase-Like Protein 1 3 4
  • Indoleamine 2,3-Dioxygenase-Like Protein 1 3 4
  • Indoleamine-Pyrrole 2,3 Dioxygenase-Like 1 2 3
  • INDOL1 3 4
  • IDO-2 3 4
  • Indoleamine 2,3-Dioxygenase-Like 1 Protein 3
  • EC 1.13.11.- 4

External Ids for IDO2 Gene

Previous HGNC Symbols for IDO2 Gene

  • INDOL1

Previous GeneCards Identifiers for IDO2 Gene

  • GC08P039913
  • GC08P039792
  • GC08P038325

Summaries for IDO2 Gene

Entrez Gene Summary for IDO2 Gene

  • Along with the enzymes encoded by the INDO (MIM 147435) and TDO2 (MIM 191070) genes, the enzyme encoded by the INDOL1 gene metabolizes tryptophan in the kynurenine pathway (Ball et al., 2007 [PubMed 17499941]).[supplied by OMIM, Feb 2011]

GeneCards Summary for IDO2 Gene

IDO2 (Indoleamine 2,3-Dioxygenase 2) is a Protein Coding gene. Among its related pathways are Tryptophan metabolism and Metabolism. Gene Ontology (GO) annotations related to this gene include heme binding and indoleamine 2,3-dioxygenase activity.

UniProtKB/Swiss-Prot Summary for IDO2 Gene

  • Catalyzes the first and rate limiting step of the catabolism of the essential amino acid tryptophan along the kynurenine pathway (PubMed:17671174). Involved in immune regulation. May not play a significant role in tryptophan-related tumoral resistance (PubMed:25691885).

Additional gene information for IDO2 Gene

No data available for CIViC Summary , Tocris Summary , Gene Wiki entry , PharmGKB "VIP" Summary , Rfam classification and piRNA Summary for IDO2 Gene

Genomics for IDO2 Gene

GeneHancer (GH) Regulatory Elements for IDO2 Gene

Promoters and enhancers for IDO2 Gene
- Elite GeneHancer and/or Elite GeneHancer-gene association Download GeneHancer data from 2017 publication | Request up-to-date GeneHancer data (full dataset)

GeneHancers around IDO2 on UCSC Golden Path with GeneCards custom track

Cistromic (ChIP-Seq) regulation report from SPP (The Signaling Pathways Project) for IDO2

Top Transcription factor binding sites by QIAGEN in the IDO2 gene promoter:
  • C/EBPalpha
  • CHOP-10
  • FOXO1
  • FOXO1a
  • GR
  • GR-alpha
  • GR-beta
  • LUN-1
  • NF-kappaB1
  • POU3F2

Genomic Locations for IDO2 Gene

Genomic Locations for IDO2 Gene
81,778 bases
Plus strand
81,778 bases
Plus strand

Genomic View for IDO2 Gene

Genes around IDO2 on UCSC Golden Path with GeneCards custom track

Cytogenetic band:
IDO2 Gene in genomic location: bands according to Ensembl, locations according to GeneLoc (and/or Entrez Gene and/or Ensembl if different)
Genomic Location for IDO2 Gene
GeneLoc Logo Genomic Neighborhood Exon StructureGene Density

RefSeq DNA sequence for IDO2 Gene

Proteins for IDO2 Gene

  • Protein details for IDO2 Gene (UniProtKB/Swiss-Prot)

    Protein Symbol:
    Recommended name:
    Indoleamine 2,3-dioxygenase 2
    Protein Accession:
    Secondary Accessions:
    • A4UD41
    • F5H5G0

    Protein attributes for IDO2 Gene

    420 amino acids
    Molecular mass:
    47075 Da
    Name=heme; Xref=ChEBI:CHEBI:30413;
    Quaternary structure:
    No Data Available
    • IDO1 and IDO2 are 2 distinct enzymes which catalyze the same reaction. IDO2 affinity for tryptophan is much lower than that of IDO1. 50 % of Caucasians harbor polymorphisms which abolish IDO2 enzymatic activity. IDO2 is expressed in human tumors in an inactive form: tryptophan degradation is entirely provided by IDO1 in these cells (PubMed:18418598). IDO2 may play a role as a negative regulator of IDO1 by competing for heme-binding with IDO1 (PubMed:25394548). Low efficiency IDO2 enzymes have been conserved throughout vertebrate evolution, whereas higher efficiency IDO1 enzymes are dispensable in many lower vertebrate lineages (PubMed:25950090). IDO1 may have arisen by gene duplication of a more ancient proto-IDO gene before the divergence of marsupial and eutherian (placental) mammals.

    Alternative splice isoforms for IDO2 Gene


neXtProt entry for IDO2 Gene

Post-translational modifications for IDO2 Gene

  • Modification sites at PhosphoSitePlus
  • Modification sites at neXtProt

Other Protein References for IDO2 Gene

ENSEMBL proteins:
REFSEQ proteins:

No data available for DME Specific Peptides for IDO2 Gene

Domains & Families for IDO2 Gene

Gene Families for IDO2 Gene

Human Protein Atlas (HPA):
  • Predicted intracellular proteins

Protein Domains for IDO2 Gene

Suggested Antigen Peptide Sequences for IDO2 Gene

GenScript: Design optimal peptide antigens:
  • Indoleamine-pyrrole 2,3-dioxygenase-like protein 1 (I23O2_HUMAN)

Graphical View of Domain Structure for InterPro Entry



  • Belongs to the indoleamine 2,3-dioxygenase family.
  • Belongs to the indoleamine 2,3-dioxygenase family.
genes like me logo Genes that share domains with IDO2: view

Function for IDO2 Gene

Molecular function for IDO2 Gene

UniProtKB/Swiss-Prot Function:
Catalyzes the first and rate limiting step of the catabolism of the essential amino acid tryptophan along the kynurenine pathway (PubMed:17671174). Involved in immune regulation. May not play a significant role in tryptophan-related tumoral resistance (PubMed:25691885).
UniProtKB/Swiss-Prot CatalyticActivity:
Reaction=L-tryptophan + O2 = N-formyl-L-kynurenine; Xref=Rhea:RHEA:24536, ChEBI:CHEBI:15379, ChEBI:CHEBI:57912, ChEBI:CHEBI:58629; Evidence=. ;.
UniProtKB/Swiss-Prot EnzymeRegulation:
Activity is inhibited by D-1MT (1-methyl-D-tryptophan) and MTH-trp (methylthiohydantoin-DL-tryptophan) but not L-1MT (1-methyl-L-tryptophan).

Enzyme Numbers (IUBMB) for IDO2 Gene

Phenotypes From GWAS Catalog for IDO2 Gene

Gene Ontology (GO) - Molecular Function for IDO2 Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0004833 tryptophan 2,3-dioxygenase activity IBA 21873635
GO:0016491 oxidoreductase activity IEA --
GO:0020037 heme binding IEA --
GO:0033754 indoleamine 2,3-dioxygenase activity ISS,IEA 17499941
GO:0046872 metal ion binding IEA --
genes like me logo Genes that share ontologies with IDO2: view
genes like me logo Genes that share phenotypes with IDO2: view

Animal Models for IDO2 Gene

MGI Knock Outs for IDO2:
  • Ido2 Ido2<tm1.2Gcp>

Animal Model Products

CRISPR Products

Clone Products

  • Addgene plasmids for IDO2

No data available for Human Phenotype Ontology , Transcription Factor Targets and HOMER Transcription for IDO2 Gene

Localization for IDO2 Gene

Subcellular locations from

Extracellular space Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi Apparatus Nucleus Mitochondrion 0 1 2 3 4 5 Confidence
COMPARTMENTS Subcellular localization image for IDO2 gene
Compartment Confidence
cytosol 4
extracellular 2
nucleus 2
plasma membrane 1
cytoskeleton 1
mitochondrion 1
peroxisome 1
endoplasmic reticulum 1
endosome 1
lysosome 1

Gene Ontology (GO) - Cellular Components for IDO2 Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0005737 cytoplasm ISS,IEA 17499941
GO:0005829 cytosol TAS --
genes like me logo Genes that share ontologies with IDO2: view

No data available for Subcellular locations from UniProtKB/Swiss-Prot and Subcellular locations from the Human Protein Atlas (HPA) for IDO2 Gene

Pathways & Interactions for IDO2 Gene

genes like me logo Genes that share pathways with IDO2: view

UniProtKB/Swiss-Prot Q6ZQW0-I23O2_HUMAN

  • Pathway: Amino-acid degradation; L-tryptophan degradation via kynurenine pathway; L-kynurenine from L-tryptophan: step 1/2.

Gene Ontology (GO) - Biological Process for IDO2 Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0002376 immune system process IEA --
GO:0006569 tryptophan catabolic process TAS --
GO:0019441 tryptophan catabolic process to kynurenine IBA,ISS 17499941
GO:0034354 'de novo' NAD biosynthetic process from tryptophan IBA 21873635
GO:0055114 oxidation-reduction process IEA --
genes like me logo Genes that share ontologies with IDO2: view

No data available for SIGNOR curated interactions for IDO2 Gene

Drugs & Compounds for IDO2 Gene

(10) Drugs for IDO2 Gene - From: ApexBio and HMDB

Name Status Disease Links Group Role Mechanism of Action Clinical Trials
Oxygen Approved, Vet_approved Pharma 0
Melatonin Approved, Vet_approved Nutra Antagonist, Full agonist, Agonist Melatonin receptors MT inhibitor, Endogenous hormone; agonist at MT1 and MT2 374
Oxitriptan Approved, Investigational Nutra Inhibition, Inhibitor 0
Tryptophan Approved, Withdrawn Nutra Positive, Allosteric regulator, Inhibition, Inhibitor 97
Serotonin Investigational Nutra 4422

(5) Additional Compounds for IDO2 Gene - From: HMDB

Name Synonyms Role CAS Number PubChem IDs PubMed IDs
  • AFMK
  • Formyl-N-acetyl-5-methoxykynurenamine
  • N-Acetyl-N-formyl-5-methoxykynurenamine
  • N-[3-(2-formamido-5-Methoxy-phenyl)-3-oxo-propyl]acetamide
  • N1-Acetyl-N2-formyl-5-methoxykynurenine
  • 3-(N-Acetylaminoethyl)-6-hydroxy-5-methoxyindole
  • N-(2(6-Hydroxy-5-methoxy-1H-indol-3-yl)ethyl)acetamide
  • N-(2-(6-Hydroxy-5-methoxyindol-3-yl)ethyl)-acetamide
  • N-(2-(6-Hydroxy-5-methoxy-1H-indol-3-yl)ethyl)-acetamide
  • N-[2-(6-Hydroxy-5-methoxy-1H-indol-3-yl)ethyl]-acetamide
  • 3-(2-Formamidobenzoyl)-L-alanine
  • N'-formylkynurenine
  • N-Formylkynurenine
  • 3-(2-Formamidobenzoyl)alanine
  • Formylkynurenine
  • 3-(N-Formylanthraniloyl)-alanine
  • alpha-amino-2-(formylamino)-gamma-oxo-Benzenebutanoate
  • alpha-amino-2-(formylamino)-gamma-oxo-Benzenebutanoic acid

(4) ApexBio Compounds for IDO2 Gene

Compound Action Cas Number
IDO inhibitor 1 Indoleamine-2,3-dioxygenase inhibitor 1204669-37-3
INCB024360 Potent IDO1 inhibitor 914471-09-3
Indoximod (NLG-8189) Indoleamine 2,3-dioxygenase (IDO) pathway inhibitor Potent and selective HDAC6 inhibitor 110117-83-4
NLG919 Potent IDO pathway inhibitor 1402836-58-1
genes like me logo Genes that share compounds with IDO2: view

Drug Products

Transcripts for IDO2 Gene

mRNA/cDNA for IDO2 Gene

6 NCBI additional mRNA sequence :
4 Ensembl transcripts including schematic representations, and UCSC links to gene/alias where relevant :

CRISPR Products

Clone Products

  • Addgene plasmids for IDO2

Alternative Splicing Database (ASD) splice patterns (SP) for IDO2 Gene

No ASD Table

Relevant External Links for IDO2 Gene

GeneLoc Exon Structure for

Expression for IDO2 Gene

mRNA expression in normal human tissues from GTEx, Illumina, BioGPS, and SAGE for IDO2 Gene

mRNA differential expression in normal tissues according to GTEx for IDO2 Gene

This gene is overexpressed in Liver (x28.7), Thyroid (x7.7), and Testis (x6.3).

Integrated Proteomics: protein expression in normal tissues and cell lines from ProteomicsDB and MOPED for IDO2 Gene

Protein tissue co-expression partners for IDO2 Gene

Transcriptomic regulation report from SPP (The Signaling Pathways Project) for IDO2

SOURCE GeneReport for Unigene cluster for IDO2 Gene:


mRNA Expression by UniProt/SwissProt for IDO2 Gene:

Tissue specificity: Detected in liver, small intestine, spleen, placenta, thymus, lung, brain, kidney, and colon (PubMed:17671174). Also expressed at low level in testis and thyroid. Not expressed in the majority of human tumor samples (>99%) (PubMed:25691885).
genes like me logo Genes that share expression patterns with IDO2: view

No data available for mRNA expression in embryonic tissues and stem cells from LifeMap Discovery , Protein differential expression in normal tissues , Evidence on tissue expression from TISSUES and Phenotype-based relationships between genes and organs from Gene ORGANizer for IDO2 Gene

Orthologs for IDO2 Gene

This gene was present in the common ancestor of animals and fungi.

Orthologs for IDO2 Gene

Organism Taxonomy Gene Similarity Type Details
(Pan troglodytes)
Mammalia IDO2 31 30
  • 99.01 (n)
(Canis familiaris)
Mammalia IDO2 31 30
  • 83.91 (n)
(Bos Taurus)
Mammalia IDO2 31 30
  • 79.85 (n)
(Rattus norvegicus)
Mammalia Ido2 30
  • 78.45 (n)
(Mus musculus)
Mammalia Ido2 17 31 30
  • 76.78 (n)
(Monodelphis domestica)
Mammalia IDO2 31
  • 73 (a)
(Ornithorhynchus anatinus)
Mammalia IDO2 31
  • 68 (a)
(Gallus gallus)
Aves INDOL1 30
  • 64.43 (n)
IDO2 31
  • 60 (a)
(Anolis carolinensis)
Reptilia IDO2 31
  • 55 (a)
tropical clawed frog
(Silurana tropicalis)
Amphibia ido1 30
  • 57.88 (n)
African clawed frog
(Xenopus laevis)
Amphibia Xl.1465 30
(Danio rerio)
Actinopterygii ido1 31 30
  • 59.01 (n)
baker's yeast
(Saccharomyces cerevisiae)
Saccharomycetes BNA2 31
  • 29 (a)
Species where no ortholog for IDO2 was found in the sources mined by GeneCards:
  • A. gosspyii yeast (Ashbya gossypii)
  • Actinobacteria (Mycobacterium tuberculosis)
  • African malaria mosquito (Anopheles gambiae)
  • Alicante grape (Vitis vinifera)
  • alpha proteobacteria (Wolbachia pipientis)
  • amoeba (Dictyostelium discoideum)
  • Archea (Pyrococcus horikoshii)
  • barley (Hordeum vulgare)
  • beta proteobacteria (Neisseria meningitidis)
  • bread mold (Neurospora crassa)
  • Chromalveolata (Phytophthora infestans)
  • common water flea (Daphnia pulex)
  • corn (Zea mays)
  • E. coli (Escherichia coli)
  • filamentous fungi (Aspergillus nidulans)
  • Firmicute bacteria (Streptococcus pneumoniae)
  • fission yeast (Schizosaccharomyces pombe)
  • fruit fly (Drosophila melanogaster)
  • green algae (Chlamydomonas reinhardtii)
  • honey bee (Apis mellifera)
  • K. lactis yeast (Kluyveromyces lactis)
  • loblloly pine (Pinus taeda)
  • malaria parasite (Plasmodium falciparum)
  • medicago trunc (Medicago Truncatula)
  • moss (Physcomitrella patens)
  • orangutan (Pongo pygmaeus)
  • pig (Sus scrofa)
  • rainbow trout (Oncorhynchus mykiss)
  • rice (Oryza sativa)
  • rice blast fungus (Magnaporthe grisea)
  • schistosome parasite (Schistosoma mansoni)
  • sea anemone (Nematostella vectensis)
  • sea squirt (Ciona intestinalis)
  • sea squirt (Ciona savignyi)
  • sea urchin (Strongylocentrotus purpuratus)
  • sorghum (Sorghum bicolor)
  • soybean (Glycine max)
  • stem rust fungus (Puccinia graminis)
  • sugarcane (Saccharum officinarum)
  • thale cress (Arabidopsis thaliana)
  • tomato (Lycopersicon esculentum)
  • toxoplasmosis (Toxoplasma gondii)
  • Trichoplax (Trichoplax adhaerens)
  • wheat (Triticum aestivum)
  • worm (Caenorhabditis elegans)

Evolution for IDO2 Gene

Gene Tree for IDO2 (if available)
Gene Tree for IDO2 (if available)
Evolutionary constrained regions (ECRs) for IDO2: view image

Paralogs for IDO2 Gene

(1) SIMAP similar genes for IDO2 Gene using alignment to 3 proteins:

  • I23O2_HUMAN
  • F5H5G0_HUMAN
  • L8E9C5_HUMAN
genes like me logo Genes that share paralogs with IDO2: view

No data available for Paralogs for IDO2 Gene

Variants for IDO2 Gene

Polymorphic Variants from UniProtKB/Swiss-Prot for IDO2 Gene

The variant Trp-248 (p.R248W) drastically reduces the enzymatic activity (PubMed:17671174, PubMed:18418598). The Del359-420 variant (p.Y359X) generates a truncated, enzymatically inactive protein (PubMed:17671174). The high prevalence of these polymorphic alleles results in a non-functional IDO2 enzyme in up to 50% of Caucasians (PubMed:18418598).

Sequence variations, with clinical significance, from ClinVar and Humsavar, with links to dbSNP for IDO2 Gene

SNP ID Clinical significance and condition Chr 08 pos Variation AA Info Type
rs10109853 - p.Arg248Trp

Additional dbSNP identifiers (rs#s) for IDO2 Gene

Structural Variations from Database of Genomic Variants (DGV) for IDO2 Gene

Variant ID Type Subtype PubMed ID
esv1987205 CNV deletion 18987734
esv2663657 CNV deletion 23128226
esv2677111 CNV deletion 23128226
esv2736908 CNV deletion 23290073
esv3572695 CNV loss 25503493
esv3616963 CNV loss 21293372
esv3616964 CNV loss 21293372
nsv1020859 CNV gain 25217958
nsv611087 CNV loss 21841781
nsv611088 CNV loss 21841781

Variation tolerance for IDO2 Gene

Gene Damage Index Score: 23.62; 99.57% of all genes are more intolerant (likely to be disease-causing)

Additional Variant Information for IDO2 Gene

Human Gene Mutation Database (HGMD)
SNPedia medical, phenotypic, and genealogical associations of SNPs for

SNP Genotyping and Copy Number Assay Products

Disorders for IDO2 Gene

Additional Disease Information for IDO2

Genetic Association Database
Human Genome Epidemiology Navigator
ATLAS of Genetics and Cytogenetics in Oncology and Haematology

No disorders were found for IDO2 Gene.

No data available for MalaCards , UniProtKB/Swiss-Prot and Genatlas for IDO2 Gene

Publications for IDO2 Gene

  1. Heme-binding-mediated negative regulation of the tryptophan metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) by IDO2. (PMID: 25394548) Lee YK … Choi EY (Experimental & molecular medicine 2014) 3 4 54
  2. Genotyping and expression analysis of IDO2 in human pancreatic cancer: a novel, active target. (PMID: 19476837) Witkiewicz AK … Brody JR (Journal of the American College of Surgeons 2009) 3 41 54
  3. Characterization of an indoleamine 2,3-dioxygenase-like protein found in humans and mice. (PMID: 17499941) Ball HJ … Hunt NH (Gene 2007) 3 4 54
  4. Novel tryptophan catabolic enzyme IDO2 is the preferred biochemical target of the antitumor indoleamine 2,3-dioxygenase inhibitory compound D-1-methyl-tryptophan. (PMID: 17671174) Metz R … Prendergast GC (Cancer research 2007) 3 4 54
  5. The human indoleamine 2,3-dioxygenase gene and related human genes. (PMID: 17430106) Murray MF (Current drug metabolism 2007) 3 23 54

Products for IDO2 Gene

Sources for IDO2 Gene