Enzymatic antioxidant superoxide dismutase

The antioxidant system in humans is a complex network composed by several enzymatic and nonenzymatic antioxidants. In addition to being an antioxidant, lycopene also exerts indirect antioxidant properties by inducing the production of cellular enzymes such as superoxide dismutase, glutathione S-transferase, and quinone reductase that also protect cells from reactive oxygen species and other electrophilic molecules (Goo and others 2007). 

Antioxidants are substances which keep oxygen radicals or reactive oxygen intermediates (ROI) under control by means of subtle time- and concentration-specific inactivation. This can be the result of enzymatic or non-enzymatic processes. The most important antioxidants in this respect are catalase, superoxide dismutase and glutathione peroxidase as well as DNA repair enzymes (such as DNA glycosylases, endonucleases and DNA ligases) in close cooperation with p 53. 

It was not until thirty years after the copper-containing protein erythrocuprein was discovered (T. Mann, D. Kei-LiNG, 1939) that its enzymatic nature was proved. At that time, this protein was shown to convert superoxide radicals into molecular oxygen and H2O2 (J.M. McCord, 1969 I. Fridovich, 1969) it was Eridovich who coined the term superoxide dismutase (SOD). This presumably most important of antioxidants accelerates the conversion of superoxide radicals 10,000 times more effectively than spontaneous dismutation. 

Gerdin E, Tyden O, Eriksson UJ. The development of antioxidant enzymatic defense in the perinatal rat lung. Activities of superoxide dismutase, glutathione peroxidase and catalase. Pediatr Res 19 (1985) 687-691. 

The four important enzymatic components of the cellular antioxidant defense system. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide (02-) to peroxide. Catalase reduces peroxide to H20. GSH peroxidase also detoxifies peroxide by reducing it to H20. GSH reductase re-reduces the oxidized glutathione (GSSG) to GSH. The NADPH required for the reduction of GSSG to GSH is primarily supplied by the oxidation of glucose via the pentose phosphate pathway. (Based on Mottet, N.K., Ed. Environmental Pathology. Oxford University Press, New York, 1985.)... 

As acute strenuous exercise and chronic exercise training increase the requirement for various antioxidants, it is conceivable that dietary supplementation of specific antioxidants would be beneficial. Older subjects may be more susceptible to oxidative stress and may benefit from the antioxidant protection provided by vitamin E. During severe oxidative stress such as strenuous exercise, the enzymatic and nonenzymatic antioxidant systems of skeletal muscle are not able to cope with the massive free-radical formation, which results in an increase in lipid peroxidation. Vitamin E decreases exercise-induced lipid peroxidation. The exercise may increase superoxide anion generation in the heart, and the increase in the activity of superoxide dismutase (SOD) in skeletal muscle may be... 

The enzymatic antioxidants are (a) catalase and the various peroxidases, whose presence lowers the concentration of hydrogen peroxide, thereby preventing it from entering into potentially damaging reactions with various cell components (see Section VI and Reactions 5.82 and 5.83), and (b) the superoxide dismutases, whose presence provides protection against dioxygen toxicity that is believed to be mediated by the superoxide anion, 62 (see Section VII and Reaction 5.95). 

The term antioxidant refers to a substance which can significantly prevent, stop and/or delay the oxidation of the oxidizable materials as well as cellular organelles via prevention and/or inhibition of chain reactions [25, 26]. In living systems, there is a multiple range of antioxidants such as different antioxidant enzymes (such as catalase, superoxide dismutase, glutathione peroxidases, etc.) as well as non-enzymatic antioxidants (such as glutathione, L-ascorbic acid, a-tocopherol, etc.) [27-29]. However, insufficient antioxidant defense systems... 

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