Inhibitors of human Indoleamine 2,3-Dioxygenase

A high throughput screen was developed to monitor indoleamine 2,3-dioxygenase (IDO) activity in vivo and in vitro. With the in vitro assay, we　identified new IDO inhibitors that have submicromolar inhibition and are not substrate analogues of IDO.  The in vivo assay was based on restriction of yeast growth caused by expression of IDO in a Saccharomyces cerevisiae tryptophan auxotroph. The evolutionary relationship of IDO to some gastropod myoglobins suggests that IDO may undergo autoxidation in the cytoplasm. To test this hypothesis, yeast knockout mutants were constructed and used in combination with the yeast growth assay for IDO activity in vivo to demonstrate a role for cytochrome b5 and cytochrome b5 reductase in maintaining IDO activity in vivo.