Cytochrome b5 is a major reductant in vivo of human indoleamine 2,3-dioxygenase expressed in yeast

The evolutionary relationship of indoleamine 2,3-dioxygenase (IDO) to some gastropod myoglobins suggests that IDO may undergo autoxidation in vivo such that one or more currently unidentified electron donors are required to maintain IDO heme iron in the active, ferrous state. To evaluate this hypothesis we have used yeast knockout mutants in combination with a recently developed yeast growth assay for IDO activity in vivo to demonstrate a role for cytochrome b(5) and cytochrome b(5) reductase in maintaining IDO activity in vivo. (c) 2006 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.