A REVIEW OF GLUTATHIONE PEROXIDASE ROLE IN THE ANTIOXIDANT PROTECTION OF THE ANIMAL ORGANISM

摘要

The selenoproteins are the most efficient endogenous components of the antioxidant defence system against reactive oxygen metabolites and their toxic products. Glutathione peroxidase (EC 1.11.1.9, GPx) was the first identified and is the most abundantselenoprotein in mammals. This review considers its; structure, distribution, biological function, and the effects of selenium and vitamin E concentrations, on the activity of GPx. Four glutathione peroxidase enzymes have been found in different cell fractions and tissues of the body (cytosolic glutathione peroxidase, GPx-1; gastrointestinal glutathione peroxidase, GPx-2; plasma glutathione peroxidase, GPx-3; and phospholipid hydroperoxide glutathione peroxidase, and GPx-4). Epididymal secretory glutathione peroxidase (GPx-5) and Se-independent GPx occupy a special position in the GPx family. GPx-5 is a secreted enzyme with the absence of the selenocysteine residue at the active site. Selenium-independent GPx is the glutathione S-transferase which cancatalyze the reduction of organic hydroperoxides, but not hydrogen peroxide. The functions of the GPxs were originally studied by changing dietary selenium levels. Selenium from organic sources is more efficiently incorporated into tissues than those from inorganic ones. The body's selenium status is assessed by the direct measurement of selenium concentration in blood and tissues, or indirectly by measuring the activity of GPx. The nutrition is one of the important factors which, besides selenium, influence enzyme activity. The effects of selenium deficiency in farm animals, which has been linked tomany health problems mainly in young animals, also have been known to reduce the productive and reproductive abilities of these animals. The deficiency of selenium may also result in immune and endocrine disorders, especially thyroid dysfunction.