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Comp Biochem Physiol B Biochem Mol Biol. 2010 Sep;157(1):10-5. doi: 10.1016/j.cbpb.2010.04.006. Epub 2010 Apr 23.

1-L-methyltryptophan is a more effective inhibitor of vertebrate IDO2 enzymes than 1-D-methyltryptophan.

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Laboratory of Biochemistry, Department of Applied Science, Faculty of Science, National University Corporation Kochi University, Kochi 780-8520, Japan.


1-D-methyltryptophan (D-1MT) is an effective anti-cancer agent in mouse tumour models. It has been suggested to be a selective inhibitor of the recently described tryptophan-degrading enzyme indoleamine 2,3-dioxygenase 2 (IDO2) rather than the closely related enzyme IDO1. We found that mammalian (mouse, opossum and platypus), chicken, frog, and fish IDO2 could be functional tryptophan-catabolising enzymes. The characteristics of pH-dependent activity and inhibitor selectivity were conserved amongst the vertebrate IDO2 proteins tested. Like IDO1 enzymes, the enzymatic activity of all IDO2s was inhibited by L-1MT but not by D-1MT in a cell-free assay. When IDO2s were expressed in mammalian cells, L-1MT was also a better inhibitor than D-1MT.

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