title: Indoleamine 2,3-dioxygenase-2; a new enzyme in the kynurenine pathway.
abstract: The kynurenine pathway of tryptophan metabolism converts the amino acid tryptophan into a number of biologically active metabolites. The first and rate-limiting step in this pathway is the conversion of tryptophan to N-formylkynurenine and until recently this reaction was thought to be performed by either of two enzymes, tryptophan 2,3-dioxygenase and indoleamine 2,3-dioxygenase. A third enzyme, indoleamine 2,3-dioxygenase-2, indoleamine 2,3-dioxygenase-like protein or proto-indoleamine 2,3-dioxygenase (IDO2, IDO-2, INDOL1 or proto-IDO), with this activity recently has been described. The gene encoding IDO2 is adjacent and structurally similar to the indoleamine 2,3-dioxygenase gene and both mouse genes use multiple promoters to express transcripts with alternate 5' exons. The IDO2 protein is expressed in the murine kidney, liver, male and female reproductive system. The two IDO enzymes can utilise a similar range of substrates, however they differ in their selectivity for some inhibitors. The selective inhibition of IDO2 by 1-methyl-D-tryptophan suggests that IDO2 activity may have a role in the inhibition of immune responses to tumours.
authors.affiliation: Discipline of Pathology and Bosch Institute, University of Sydney, Camperdown, NSW 2006, Australia. helenb@med.usyd.edu.au
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Ball
authors.forename: Hajime J
authors.initials: HJ
authors.lastname: Yuasa
authors.forename: Christopher J D
authors.initials: CJ
authors.lastname: Austin
authors.forename: Silvia
authors.initials: S
authors.lastname: Weiser
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Hunt
mesh_terms: D000818:Animals; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D007737:Kynurenine / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D008297:Male; D051379:Mice; D012098:Reproduction / Q000502:physiology; D013379:Substrate Specificity; D014364:Tryptophan / Q000031:analogs & derivatives / Q000378:metabolism*; D014366:Tryptophan Oxygenase / Q000037:antagonists & inhibitors
chemical_list: D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D007737:Kynurenine; D014364:Tryptophan; D014366:Tryptophan Oxygenase