Hydrogen superoxide dismutase (SOD) is an enzyme that catalyzes the conversion reactions of the active oxygen radical (Ο2-) to either molecular oxygen (Ο2) or hydrogen superoxide (H2O2). Reactive oxygen species are produced as a byproduct of oxygen metabolism and if left untreated can cause many types of cell damage. Hydrogen peroxide, which is also harmful to the cell, is broken down by other enzymes such as catalase. Thus, SOD is an important antioxidant defense in almost all cells that use oxygen.
The measurement of superoxide dismutase in the context of Oxidative Stress tests can help identify the underlying causes for many diseases and clinical disorders, so as to design the appropriate individualized therapeutic interventions.
There are two types of SOD in terms of the presence of metals in the enzyme molecule: copper/zinc (Cu/Zn) SOD and manganese (Mn) SOD. Each type of SOD plays a different role in maintaining cell health. Cu/Zn SOD protects the cytoplasm of cells and Mn SOD protects mitochondria from the harmful effects of free radicals. There are 2 other types of SOD, iron (Fe) SOD and nickel (Ni) SOD, but they do not exist in humans. Regarding the polypeptide chains of SOD, there are 3 forms: SOD1, whose gene is located on chromosome 21, is dimeric, contains copper and zinc, and is located in the cytoplasm, SOD2, whose gene is located on chromosome 6, is tetrameric, contains manganese and is located in the mitochondria and SOD3 whose gene is located on chromosome 4, is tetrameric, contains copper and zinc and is found extracellularly.
Studies have shown that SOD acts as an antioxidant and anti-inflammatory enzyme in the body, neutralizing free radicals that can lead to precancerous changes in cells. There is strong research interest in the potential of superoxide dismutase as an anti-aging treatment, as it is now known that SOD levels decrease, while free radical levels increase as a person ages. The SOD found in both the dermis and the epidermis is the key to the production of fibroblasts (cells involved in skin formation).
Abnormalities in the Cu/Zn SOD gene (SOD1) may contribute to the development of Amyotrophic Lateral Sclerosis (ALS) or Lou Gehrig disease in some people. ALS is a deadly disease that causes damage to motor nerve cells in the brain and spinal cord. Low levels of superoxide dismutase in patients with ALS are thought to leave nerve cells unprotected from free radicals that can damage them. That's why researchers are studying the effect of vitamin E and other antioxidant supplements on controlling this disease.
Increased production of SOD1 has been linked to the nervous disorders seen in Down syndrome. In patients with thalassemia, SOD may be elevated. Studies in humans show that plasma SOD may be an indicator of cardiovascular changes in hypertensive and diabetic patients, as changes in its levels are associated with changes in patients' vascular structure and function.
The physiological significance of SOD is evident from the serious effects that occur in genetically modified mice that lack these enzymes. SOD2-deficient mice die a few days after birth, amid massive oxidative stress. Mice lacking SOD1 develop a wide range of pathologies, including hepatocellular carcinoma, accelerated age-related muscle mass loss, cataract onset, and reduced lifespan. Mice that do not have SOD3 do not show significant damage and have a normal lifespan, although they are more susceptible to oxidative damage. Laboratory animals without SOD are generally more susceptible to the lethal effects of peroxide-producing compounds, such as various herbicides.
Superoxide dismutase has been used to treat arthritis, prostate hypertrophy, corneal ulcers, burns, inflammatory diseases and especially inflammatory bowel disease, long-term damage from exposure to tobacco and radiation, and preventing the side effects of anti-cancer therapies. Topical administration of superoxide dismutase can help reduce wrinkles on the face, scars, treat wounds and burns, skin discolorations, and protection from harmful UV rays. For therapeutic purposes, SOD is injected topically.
Superoxide dismutase is found in barley, broccoli, Brussels sprouts, cabbage, and most green leafy vegetables. There is no evidence that eating foods rich in SOD or SOD supplements can have any health effect as it breaks down into amino acids before being absorbed (with the possible exception of SOD which is bound to wheat proteins such as gliadin). However, the body needs the building blocks of the enzyme as well as plenty of vitamin C and copper to make it.