Heme-containing dioxygenases involved in tryptophan oxidation

Heme iron is often used in biology for activation of oxygen. The mechanisms of oxygen activation by heme-containing monooxygenases (the cytochrome P450s) are well known, and involve formation of a Compound I species, but information on the heme-containing dioxygenase enzymes involved in tryptophan oxidation lags far behind. In this review, we gather together information emerging recently from structural, mechanistic, spectroscopic, and computational approaches on the heme dioxygenase enzymes involved in tryptophan oxidation. We explore the subtleties that differentiate various heme enzymes from each other, and use this to piece together a developing picture for oxygen activation in this particular class of heme-containing dioxygenases.

► This review looks at the heme-containing enzymes involved in tryptophan oxidation. ► Indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase are the main enzymes considered. ► Comparisons are made with other heme enzymes that use oxygen to activate substrates.