Aerobic organisms reactive oxygen species

All aerobic organisms contain substances that help prevent injury mediated by free radicals, and these include antioxidants such as a-tocopherol and the enzymes superoxide dismutase and glutathione peroxidase. When the protective effect of the antioxidants is overwhelmed by the production of reactive oxygen species, the intracellular milieu becomes oxidative, leading to a state known as oxidative stress (Halliwell and Gutteridge, 1999). Thus the balance between the generated free radicals and the efficiency of the protective antioxidant system determines the extent of cellular damage. 

Superoxide Reductase (see Iron Proteins with Mononuclear Active Sites). Detoxification of reactive oxygen species in anaerobic microorganisms has recently been shown to center around SOR, a novel mononuclear iron enzyme that reduces superoxide to hydrogen peroxide (see equation 4), rather than dismuting superoxide to oxygen and hydrogen peroxide as is the case for the superoxide dismutases found in aerobic organisms. 

The lifetime of reactive oxygen species (ROS) is extremely short, and if a physiological acceptor does not immediately neutralize them, ROS can damage biological systems. All aerobic organisms have developed more or less complex systems to neutralize them before their potentially harmful effect is activated. Nutritional elements are also extremely important. Foods that have potential or definite antioxidant capacities are mainly vegetables and fruits, as well as beverages like red wine, tea and beer. 

In the last ten years, there has been no research area, in which the biochemical function of an enzyme was discussed so controversly and emotionally than with superoxide dismutase. There is a polarization between one group which debates the biological importance of the dismutation of superoxide and another one which is convinced that this reaction is required in aerobic metabolism, preventing the organism from an attack of reactive oxygen species. The current knowledge does not allow a definite... 

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