Lesson 33: Superoxide Dismutase (SOD) Copy

Superoxide dismutase, one of nature’s most powerful antioxidants. Superoxide dismutase (SOD) is an antioxidant enzyme that scavenges superoxide radicals, and are found in all living cells. SODs have been studied as a therapeutic tool for very diverse pathological situations for more than 30 years and, in many animal models and a few clinical trials, their use has shown positive outcomes. Superoxide dismutase (SOD) scavenges superoxide radicals, a primary type of ROS produced in the body, and hence, plays a central role in protection against oxidative stress.

Of the three genes that encode SOD in mammals (SOD1, SOD2, and SOD3), SOD1 is present largely in the cytoplasm and partly in the intermembrane space of mitochondria. Because SOD1 is the sole superoxide-scavenging enzyme in erythrocytes, in the absence of SOD1, intracellular superoxide levels have been calculated to be 200 times higher than that in ordinary erythrocytes. Thus SOD1 knockout mice develop anemia with the life span of erythrocytes shortened by approximately 60%–70% that of wild-type mice. Erythrocytes lack lysosomes but possess the UPS, although to a lesser extent compared with other nucleated cells. Indeed, the catalytic activities of proteasomes suffer from oxidative inactivation, leading to the accumulation of ubiquitinated proteins in SOD1-deficient erythrocytes. Superoxide dismutases (SOD) can contain zinc and copper (Cu-Zn-SOD) and also manganese or iron. SOD converts superoxide to hydrogen peroxide and oxygen, and minimizes production of the hydroxyl radical that causes so much damage (it is the most potent of the oxygen free radicals). This system is nearly always the antioxidant defence in cells exposed to oxygen. It is extremely quick and can more than match the production of superoxide when working properly.

There are three forms of SOD in the human body:•

SOD1 in the cytoplasm: copper and zinc (Cu-Zn-SOD).•

SOD2 in the mitochondria: manganese is found in the liver but not in erythrocytes. Free radicals in the mitochondria are byproducts of oxidative phosphorylation, which produces energy.•

SOD3 extracellular: copper and zinc (Cu-Zn-SOD).

SOD is thought to protect from free radicals produced by the ageing process and ischaemic tissue damage. It also has an effect on inflammation. Mutations in SOD1 have been linked to familial amyotrophic lateral sclerosis (ALS).