Superoxide Dismutase

Superoxide Dismutase, or SOD, is a metalloenzyme whose active center is occupied by copper and zinc, sometimes manganese or iron. SOD plays an extremely important role in the protection of all aerobic life-systems, including man, against oxygen toxicity (and the free radicals derived from oxygen).

The enzyme superoxide dismutase, or SOD, catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. SOD is an endogenously produced intracellular enzyme present in essentially every cell in the body. There are at least three forms of superoxide dismutase in nature. Human erythrocytes contain an SOD enzyme with divalent copper and divalent zinc. Chicken liver mitochondria and E. coli contain a form with trivalent manganese. E. coli also contains a form of the enzyme with trivalent iron. The Cu-Zn enzyme is a dimer of molecular weight 32,500. The two subunits are joined by a disulfide bond. Superoxide dismutases are enzymes that play major roles in the protection of cells against oxidative damage. The two major forms of superoxide dismutase (SOD) in humans are the mitochondrial manganese SOD and the cytosolic copper/zinc SOD. A copper/zinc SOD, isolated from beef liver, has been used intra-articularly for degenerative joint disorders as an anti-inflammatory agent. SOD is also marketed as a nutritional supplement.

SOD is also an effective defence weapon and Mycobacteria and Nocadia have SOD which enables them to resist the injection of superoxide by phagocytes. When these organisms cause serious disease, it takes the body a very long time to win, and depending on the strength of the patient the bacteria may win. Although the enzyme isn't especially fast relative to the spontaneous dismutation of superoxide, the ability of the enzyme to provide some protection to organisms is shown by the existence of a motor neuron disease in individuals who have point mutations in SOD and by the finding that the absence of SOD may lead to a form of anemia.

Cellular SOD is actually represented by a group of metalloenzymes with various prosthetic groups. The prevalent enzyme is cupro-zinc (CuZn) SOD, which is a stable dimeric protein (32,000 D).
SOD is an enzyme associated with copper, zinc, and manganese by body cells, and breaks down the superoxide free radicals. It is said that SOD protects the lens of the eyes by guarding against free radical damage.

Most organisms are exposed to oxygen for most of their lives. However oxygen can be converted to form that of extremely reactive radicals that bind to DNA, proteins and lipids causing permanent loss of structure to such molecules. Superoxide radicals most dangerous of which is hydroxy radical. To protect from such danger cells have superoxide dismutase and catalase enzymes. Hydrogen peroxide is itself dangerous and must be destroyed by catalase. A number of tumour cells have been found to be deficient in SOD. Initially plan was to treat this as a target for reactive radicals. Then discovered that re-expression of SOD gene cancels immortality. It seems that an essential step in becoming immortal is switch off SOD gene or maybe cluster genes that include SOD. Absence of SOD activity seems to support cancer.

SOD injection into patients with osteoarthritis of the knee is one of the most impressive examples of beneficial SOD therapy. Therapy involved 2 mg SOD three times per day produces substantial reduction in pain, normal walking ability and climbing stairs (normally too painful). Works by reducing inflammation. Phagocytes destroy cells by pumping superoxide radicals into cells and tissues, and other systems such as Ab-Ag complexes can trigger phagocytes to dump superoxide. seems to be a general alert signal to attract wbc etc to the scene causes swelling , inflammation etc. SOD mops up the superoxide.

Amyotophic Lateral Sclerosis (ALS), or Lou Gehrig’s Disease, is a crippling neuromuscular disease that usually attacks people between the ages of fifty and sixty; although, cases are reported from the early teens to the late eighties. Strong evidence links Amyotophic Lateral Sclerosis to mutations in the SOD1 gene. The gene controls the enzyme, Cu/Zn Superoxide Dismutase; this enzyme breaks down free radicals, preventing tissue damage. When the SOD gene is mutated, the enzyme is also mutated. The mutated enzyme loses its anti-oxidant affect, and it begins to exhibit peroxidaseal properties. This is a possible cause of nerve cell degeneration. Inhibiting this enzyme could slow or stop the degeneration of nerve cells, which leads to the disruption of muscle control in ALS patients. A determination of the kinetics of the mutated version of Cu/Zn Superoxide Dismutase and some of its inhibitors would be beneficial to the medical community.

As an enzyme, SOD has particular value as an antioxidant that can help to protect against cell destruction. It has the distinct ability to neutralize superoxide, one of the most damaging free radical substances in nature. Like so many other protective compounds which naturally occur in the body, it decreases with age, making cells much more vulnerable to the oxidants which cause aging and disease. It occurs naturally in broccoli, Brussels's sprouts, wheat grass and in the majority of green plants.