Superoxide Dismutases and Reactive Oxygen Species

The 'free radical theory' of aging was introduced over a half-century ago. In this theory, much of the deleterious effects of aging were attributed to the cumulative buildup of damage from reactive oxygen species. When discussing reactive oxygen species (ROS) in aerobic systems, both superoxide radicals (O2-) and superoxide dismutases (SODs) are considered to play prominent roles. O2- is formed by attachment of the electron to oxygen (O2) that is present in tens to hundreds of micromolar concentration in vivo. SODs are enzymes that serve to eliminate O2- by rapidly converting it to O2 and hydrogen peroxide (H2O2). Both the radical and the enzyme will be discussed with the focus on the systems that are present in humans.