Biological sources of reduced oxygen species

This paper reviews the various enzymatic sources of superoxide radical, hydrogen peroxide and hydroxyl radical, and their localization within the cell. In the first part, we will consider electron transfer reactions directly from a biological macromolecule (essentially reductases) to oxygen. In the second part, we will consider reactions during which electrons are transferred from the reductase to oxygen via a small molecule which behaves as a substrate of the enzymatic system.