Oxidative damage defenses against

As well as the formation of radicals, oxidative stress may also contribute to the toxicity of electrophilic metabolites. This may result from depletion by electrophiles of the glutathione pool, one of the major defenses against damage by reactive oxygen species. 

Polle, A., Defense against photooxidative damage in plants, in Oxidative Stress and the Molecular Biology of Antioxidant Defenses, Scandalios, J.G., Ed., Cold Spring Harbor Laboratory Press, New York, 1997, 623. 

The turnover rates of GSH and the activity of GSH synthetase during oxidative stress induced by butylhydroperoxide in young and mature animals have been measured. These studies have found that defense mechanisms against oxidative stress in the brain differ with age. Young people can increase the cellular availability of GSH, whereas older people can increase GSH synthetase activity during oxidative stress. These differences make older people more susceptible to brain oxidative damage. 

Superoxide dismutase and catalase are remarkably efficient, performing their reactions at or near the diffusion-limited rate (Section 8.4.2). Other cellular defenses against oxidative damage include the antioxidant vitamins, vitamins E and C. Because it is lipophilic, vitamin E is especially useful in protechng membranes from lipid peroxidahon. 

Antioxidants are naturally present in many foodstuffs and are of great importance as inactivators of radical formation. Some antioxidative enzyme systems are produced in the human body and are supposed to play an important role in the cellular defense against oxidative damage (Langseth, 1995). 

Strong evidence has been presented indicating that many of the cell alterations seen in normal aging and in various diseases, including cancer, are due to oxidative damage from active oxygen species. SODs function in the cellular defense against the active species, Oj. Study of these enzymes is therefore of potential clinical interest. 

The major enzymatic defenses against oxidative stress are provided by superoxide dismutase, glutathione peroxidase, and catalase. The wide distribution of these enzymatic activities underscores the ever present problem of oxidative damage. 

The biological defense systems protecting against oxidative damage and its consequences are summarized below. 

Oxidative damage caused by reactive oxygen species has been called oxidative stress . Biological systems contain powerful enzymatic and non-enzymatic antioxidant mechanisms, and oxidative stress denotes a shift in the pro-oxidant/antioxidant balance in favor of the former (1). Reactive oxygen species are important mediators of several forms of cell damage in parasites and this discussion will focus on the defense mechanisms of parasites against these species. 

---