| IDO2 (indolamine-2,3-dioxygenase) is an enzyme with protein size of 420 amino acids (47 kDa) that is used for catabolism of tryptophan. In organisms, other enzymes participate in L-tryptophan cleavage, namely [[Indoleamine 2,3-dioxygenase|IDO1]] and [[Tryptophan 2,3-dioxygenase|TDO]]. Despite of IDO1 and IDO2 are closely related enzymes originating by gene duplication and sharing high level (43%) of sequence homology,<ref>{{cite journal | vauthors = Yuasa HJ, Mizuno K, Ball HJ | title = Low efficiency IDO2 enzymes are conserved in lower vertebrates, whereas higher efficiency IDO1 enzymes are dispensable | journal = The FEBS Journal | volume = 282 | issue = 14 | pages = 2735–45 | date = July 2015 | pmid = 25950090 | doi = 10.1111/febs.13316 }}</ref><ref>{{cite journal | vauthors = Ball HJ, Sanchez-Perez A, Weiser S, Austin CJ, Astelbauer F, Miu J, McQuillan JA, Stocker R, Jermiin LS, Hunt NH | title = Characterization of an indoleamine 2,3-dioxygenase-like protein found in humans and mice | journal = Gene | volume = 396 | issue = 1 | pages = 203–13 | date = July 2007 | pmid = 17499941 | doi = 10.1016/j.gene.2007.04.010 }}</ref> they differentiate by their kinetics, function and expression pattern. Genes encoding IDO1 and IDO2 have similar genomic structure and are situated closely to each other on chromosome 8.<ref>{{cite journal | vauthors = Ball HJ, Sanchez-Perez A, Weiser S, Austin CJ, Astelbauer F, Miu J, McQuillan JA, Stocker R, Jermiin LS, Hunt NH | title = Characterization of an indoleamine 2,3-dioxygenase-like protein found in humans and mice | journal = Gene | volume = 396 | issue = 1 | pages = 203–13 | date = July 2007 | pmid = 17499941 | doi = 10.1016/j.gene.2007.04.010 }}</ref> IDO2 is produced in a very limited type of tissues as kidney, liver or antigen presenting cells.<ref>{{cite journal | vauthors = Merlo LM, Mandik-Nayak L | title = IDO2: A Pathogenic Mediator of Inflammatory Autoimmunity | journal = Clinical Medicine Insights. Pathology | volume = 9 | issue = Suppl 1 | pages = 21–28 | date = 2016 | pmid = 27891058 | pmc = 5119657 | doi = 10.4137/CPath.S39930 }}</ref> IDO2 is less active on substrates of IDO1, better catabolizing other Trp derivates as 5-methoxytryptophan. There are several isoforms in population that comes from alternative splicing.<ref>{{cite journal | vauthors = Metz R, Duhadaway JB, Kamasani U, Laury-Kleintop L, Muller AJ, Prendergast GC | title = Novel tryptophan catabolic enzyme IDO2 is the preferred biochemical target of the antitumor indoleamine 2,3-dioxygenase inhibitory compound D-1-methyl-tryptophan | journal = Cancer Research | volume = 67 | issue = 15 | pages = 7082–7 | date = August 2007 | pmid = 17671174 | doi = 10.1158/0008-5472.CAN-07-1872 }}</ref> As well as IDO1, IDO2 has been reported in [[Treg]] differentiation ''in vitro'',<ref>{{cite journal | vauthors = Metz R, Smith C, DuHadaway JB, Chandler P, Baban B, Merlo LM, Pigott E, Keough MP, Rust S, Mellor AL, Mandik-Nayak L, Muller AJ, Prendergast GC | title = IDO2 is critical for IDO1-mediated T-cell regulation and exerts a non-redundant function in inflammation | journal = International Immunology | volume = 26 | issue = 7 | pages = 357–67 | date = July 2014 | pmid = 24402311 | pmc = 4432394 | doi = 10.1093/intimm/dxt073 }}</ref> suggesting a role in tolerance maintenance. It's expression has been found in several cancers, gastric, colon or renal tumores.<ref>{{cite journal | vauthors = Löb S, Königsrainer A, Zieker D, Brücher BL, Rammensee HG, Opelz G, Terness P | title = IDO1 and IDO2 are expressed in human tumors: levo- but not dextro-1-methyl tryptophan inhibits tryptophan catabolism | journal = Cancer Immunology, Immunotherapy | volume = 58 | issue = 1 | pages = 153–7 | date = January 2009 | pmid = 18418598 | doi = 10.1007/s00262-008-0513-6 }}</ref> | | IDO2 (indolamine-2,3-dioxygenase) is an enzyme with protein size of 420 amino acids (47 kDa) that is used for catabolism of tryptophan. In organisms, other enzymes participate in L-tryptophan cleavage, namely [[Indoleamine 2,3-dioxygenase|IDO1]] and [[Tryptophan 2,3-dioxygenase|TDO]]. Despite of IDO1 and IDO2 are closely related enzymes originating by gene duplication and sharing high level (43%) of sequence homology,<ref>{{cite journal | vauthors = Yuasa HJ, Mizuno K, Ball HJ | title = Low efficiency IDO2 enzymes are conserved in lower vertebrates, whereas higher efficiency IDO1 enzymes are dispensable | journal = The FEBS Journal | volume = 282 | issue = 14 | pages = 2735–45 | date = July 2015 | pmid = 25950090 | doi = 10.1111/febs.13316 }}</ref><ref>{{cite journal | vauthors = Ball HJ, Sanchez-Perez A, Weiser S, Austin CJ, Astelbauer F, Miu J, McQuillan JA, Stocker R, Jermiin LS, Hunt NH | title = Characterization of an indoleamine 2,3-dioxygenase-like protein found in humans and mice | journal = Gene | volume = 396 | issue = 1 | pages = 203–13 | date = July 2007 | pmid = 17499941 | doi = 10.1016/j.gene.2007.04.010 }}</ref> they differentiate by their kinetics, function and expression pattern. Genes encoding IDO1 and IDO2 have similar genomic structure and are situated closely to each other on chromosome 8.<ref>{{cite journal | vauthors = Ball HJ, Sanchez-Perez A, Weiser S, Austin CJ, Astelbauer F, Miu J, McQuillan JA, Stocker R, Jermiin LS, Hunt NH | title = Characterization of an indoleamine 2,3-dioxygenase-like protein found in humans and mice | journal = Gene | volume = 396 | issue = 1 | pages = 203–13 | date = July 2007 | pmid = 17499941 | doi = 10.1016/j.gene.2007.04.010 }}</ref> IDO2 is produced in a very limited type of tissues as kidney, liver or antigen presenting cells.<ref>{{cite journal | vauthors = Merlo LM, Mandik-Nayak L | title = IDO2: A Pathogenic Mediator of Inflammatory Autoimmunity | journal = Clinical Medicine Insights. Pathology | volume = 9 | issue = Suppl 1 | pages = 21–28 | date = 2016 | pmid = 27891058 | pmc = 5119657 | doi = 10.4137/CPath.S39930 }}</ref> IDO2 is less active on substrates of IDO1, better catabolizing other Trp derivates as 5-methoxytryptophan. There are several isoforms in population that comes from alternative splicing.<ref>{{cite journal | vauthors = Metz R, Duhadaway JB, Kamasani U, Laury-Kleintop L, Muller AJ, Prendergast GC | title = Novel tryptophan catabolic enzyme IDO2 is the preferred biochemical target of the antitumor indoleamine 2,3-dioxygenase inhibitory compound D-1-methyl-tryptophan | journal = Cancer Research | volume = 67 | issue = 15 | pages = 7082–7 | date = August 2007 | pmid = 17671174 | doi = 10.1158/0008-5472.CAN-07-1872 }}</ref> As well as IDO1, IDO2 has been reported in [[Treg]] differentiation ''in vitro'',<ref>{{cite journal | vauthors = Metz R, Smith C, DuHadaway JB, Chandler P, Baban B, Merlo LM, Pigott E, Keough MP, Rust S, Mellor AL, Mandik-Nayak L, Muller AJ, Prendergast GC | title = IDO2 is critical for IDO1-mediated T-cell regulation and exerts a non-redundant function in inflammation | journal = International Immunology | volume = 26 | issue = 7 | pages = 357–67 | date = July 2014 | pmid = 24402311 | pmc = 4432394 | doi = 10.1093/intimm/dxt073 }}</ref> suggesting a role in tolerance maintenance. Its expression has been found in several cancers, gastric, colon or renal tumores.<ref>{{cite journal | vauthors = Löb S, Königsrainer A, Zieker D, Brücher BL, Rammensee HG, Opelz G, Terness P | title = IDO1 and IDO2 are expressed in human tumors: levo- but not dextro-1-methyl tryptophan inhibits tryptophan catabolism | journal = Cancer Immunology, Immunotherapy | volume = 58 | issue = 1 | pages = 153–7 | date = January 2009 | pmid = 18418598 | doi = 10.1007/s00262-008-0513-6 }}</ref> |
