PROSITE documentation PDOC00684
Indoleamine 2,3-dioxygenase signatures


Indoleamine 2,3-dioxygenase (EC (IDO) [1] is an enzyme responsible for the conversion of tryptophan and other indole derivatives to kynurenines. In mammals, IDO is induced by interferon-γ (IFN-γ) and responsible for some of its anti-proliferative effects. The degradative action of IDO on tryptophan leads to cell death by starvation of this essential and relatively scarce amino acid. IDO is a heme-containing enzyme of about 400 amino acids.

Other proteins that are evolutionarily related to IDO are:

  • Myoglobin from the red muscle of the gastropods Nordotis madaka and Sulculus diversicolor [2]. These unusual globins lack enzymatic activity but have kept the heme group.
  • Yeast hypothetical protein YJR078w.

As a signature for the IDO family, we selected two conserved regions. The first is located in the central section and is rich in glycine and serine residues; the second is located in the second third of the sequence and contains a conserved histidine that could serve as a proximal ligand to the heme iron.

Last update:

May 2004 / Text revised.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

IDO_1, PS00876; Indoleamine 2,3-dioxygenase signature 1  (PATTERN)

IDO_2, PS00877; Indoleamine 2,3-dioxygenase signature 2  (PATTERN)


1AuthorsTaylor M.W. Feng G.S.
TitleRelationship between interferon-gamma, indoleamine 2,3-dioxygenase, and tryptophan catabolism.
SourceFASEB J. 5:2516-2522(1991).
PubMed ID1907934

2AuthorsSuzuki T.
TitleAbalone myoglobins evolved from indoleamine dioxygenase: the cDNA-derived amino acid sequence of myoglobin from Nordotis madaka.
SourceJ. Protein Chem. 13:9-13(1994).
PubMed ID8011076

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