Superoxide dismutase

Under normal circumstances in aerobic metabolism, oxygen is reduced by four electrons, forming H2O. Although this usually occurs uneventfully, incomplete reduction will result in the generation of oxygen radicals and other reactive species. These are: the superoxide radical O2r, hydrogen peroxide (H2O2) and the hydroxyl radical (OH-). The superoxide and hydroxyl radicals are particularly reactive and can attack membrane components, nucleic acids and other cellular macromol-ecules, leading to their destruction/modification. O2r and OHr radicals, for example, are believed to be amongst the most mutagenic substances generated by ionizing radiation.

Oxygen-utilizing organisms have generally evolved specific enzyme-mediated systems that serve to protect the cell from such reactive species. These enzymes include SOD and catalase or glutathione peroxidase (GSH-px), which catalyse the following reactions:

H2O2 + H2O2 calalaseor GSH-px ) 2H2O + O2

In general, all aerobic organisms harbour these oxygen-defence systems. At least three types of SOD have been identified: a cytosolic eukaryotic dismutase, generally a 31 kDa dimer, containing both copper and zinc; a 75 kDa mithocondrial form and a 40 kDa bacterial form, each of which contains two manganese atoms. There is also an iron-containing form found in some bacteria, blue-green algae and many plants. The metal ions play a direct role in the catalytic conversion, serving as transient acceptors/donors of electrons.

In humans, increased generation of O2r and/or reduced SOD levels have been implicated in a wide range of pathological conditions, including ageing, asthma, accelerated tumour growth, neu-rodegenerative diseases and inflammatory tissue necrosis. Furthermore, administration of SOD has been found to reduce tissue damage due to irradiation, or to other conditions that generate O2r. Increased SOD production in Drosophila melanogaster leads to increased oxygen tolerance and, interestingly, increased life span.

SOD isolated from bovine liver or erythrocytes has been used medically as an anti-inflammatory agent. Human SOD has also been expressed in several recombinant systems, and is currently being evaluated to assess its ability to prevent tissue damage induced by exposure to excessively oxygen-rich blood.

Cure Tennis Elbow Without Surgery

Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

Get My Free Ebook

Post a comment