Superoxide dismutase 2, mitochondrial, also known as SOD2, is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 which in humans is encoded by the SOD2 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

Function

This gene is a member of the iron/manganese superoxide dismutase

Superoxide dismutase

Superoxide dismutases are a class of enzymes that catalyze the dismutation of superoxide into oxygen and hydrogen peroxide. As such, they are an important antioxidant defense in nearly all cells exposed to oxygen...

 family. It encodes a mitochondrial matrix protein that forms a homotetramer and binds one manganese ion per subunit. This protein transforms toxic superoxide

Superoxide

A superoxide, also known by the obsolete name hyperoxide, is a compound that possesses the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide. It is important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature...

, a byproduct of the mitochondrial electron transport chain, into hydrogen peroxide

Hydrogen peroxide

Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

 and diatomic oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

. Alternate transcriptional splice variants, encoding different isoforms, have been characterized.

Clinical significance

Mutations in this gene have been associated with idiopathic

Idiopathic

Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...

 cardiomyopathy

Cardiomyopathy

Cardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...

(IDC), sporadic motor neuron disease, and cancer. A common polymorphism associated with greater susceptibility to various patholiges is found in the mitochondrial leader targeting sequence (Val9Ala). Mice lacking Sod2 die shortly after birth, indicating that unchecked levels of superoxide are incompatible with mammalian life. However, mice 50% deficient in Sod2 have a normal lifespan and minimal phenotypic defects but do suffer increased DNA damage and increased incidence of cancer.

SOD2 and Exercise-Induced Cardioprotection

When animals are exercised at a relatively high work rate, many exercise training studies report that exercise training promotes an increase in myocardial MnSOD activity. This is significant because two recent studies reveal that increased MnSOD activity is essential to achieve optimal training-induced protection against both ischemia/reperfusion(IR)-induced cardiac arrhythmias and infarction. Specifically, using an antisense oligonucleotide against MnSOD to prevent ExTr-induced increases in myocardial MnSOD activity, Yamashita et al. demonstrated that an increase in myocardial MnSOD activity is required to provide training-induced protection against IR-induced myocardial infarction. Similarly, Hamilton et al. [10], using a MnSOD gene silencing approach, reported that prevention of the ExTr-induced increase in myocardial MnSOD resulted in a loss of training-induced protection against IR-mediated arrhythmias. In contrast to these findings, training-induced increases in cardiac MnSOD are not required to achieve training-induced cardioprotection against myocardial stunning. (Power et al. 2007)

Further reading