Abstract
Superoxide radicals are produced by the one-electron reduction of molecular oxygen. These radicals are formed physiologically as a by-product of oxygen metabolism, and they are important in toxicology as a product of the metabolism of redox-active xenobiotics. Superoxide is also produced by dedicated enzymes, and in these situations it plays a role in combatting microbial pathogens and regulating cellular processes. This article covers the properties and biological chemistry of superoxide radicals. It considers how they are produced, what biomolecules they react with, and the reactions that contribute to their toxicity. It also considers the function of superoxide dismutases, the enzymes responsible for removal of most of the superoxide produced in living organisms.