Indoleamine 2,3-dioxygenase. Purification and some properties

J Biol Chem. 1978 Jul 10;253(13):4700-6.


Indoleamine 2,3-dioxygenase was purified from rabbit small intestine to apparent homogeneity as judged by polyacrylamide gel electrophoresis and analytical ultracentrifugation. The native enzyme was a monomeric protein of a molecular weight of 41,000 +/- 1,000 with an s020,w value of 3.45 S. It had a relative abundance of hydrophobic amino acids such as valine, leucine, and isoleucine, and contained approximately 5% carbohydrate by weight. The estimated content of sugar residues per mol of enzyme was: galactose, 1.2; mannose, 2.6; N-acetylglucosamine, 5.2; and sialic acid, 0.8. One mole of enzyme had 0.8 mol of protoheme IX as a prosthetic group. However, copper was not detected in a significant amount and the ratio of copper to heme was less than 0.03. EPR spectra of the nitric oxide complex of the ferrous enzyme indicated that a nitrogen atom, possibly in an imidazole group, might be coordinated as the fifth ligand of the heme coenzyme. The anisotropic g values were gx = 2.08, gy = 1.98, and gz = 2.01. A single enzyme protein catalyzed the oxygenative ring cleavage of D- and L-tryptophan, D- and L-5-hydroxytryptophan, tryptamine, and serotonin. In addition, the purified enzyme had a peroxidase activity with guaiacol and potassium iodide as hydrogen donors, but not a catalase activity.

MeSH terms

  • Amino Acids / analysis
  • Animals
  • Electrophoresis, Disc
  • Hexoses / analysis
  • Hydrogen-Ion Concentration
  • Indoles
  • Intestine, Small / enzymology*
  • Molecular Weight
  • Oxygenases / isolation & purification
  • Oxygenases / metabolism*
  • Rabbits
  • Seasons
  • Substrate Specificity


  • Amino Acids
  • Hexoses
  • Indoles
  • Oxygenases