Glutathione peroxidase selenoprotein

Deagen JT, Butler JA, Zachara BA, et al. 1993. Determination of the distribution of selenium between glutathione peroxidase, selenoprotein P, and albumin in plasma. Anal Biochem 208(1) 176-181. 

In 1956 selenium was identified (123) as an essential micronutrient in nutrition. In conjunction with vitamin E, selenium is effective in the prevention of muscular dystrophy in animals. Sodium selenite is administered to prevent exudative diathesis in chicks, a condition in which fluid leaks out of the tissues white muscle disease in sheep and infertility in ewes (see Feed additives). Selenium lessens the incidence of pneumonia in lambs and of premature, weak, and stillborn calves controls hepatosis dietetica in pigs and decreases muscular inflammation in horses. White muscle disease, widespread in sheep and catde of the selenium-deficient areas of New Zealand and the United States, is insignificant in high selenium soil areas. The supplementation of animal feeds with selenium was approved by the U.S. FDA in 1974 (see Feed additives). Much of selenium s metabolic activity results from its involvement in the selenoprotein enzyme, glutathione peroxidase. 

Another related nonheme enzyme is the selenoprotein glutathione peroxidase. It reacts by a mechanism very different (Eq. 15-59) from those discussed... 

Selenium plays a special role in development and protection of spermatozoa (Chapter 15). Tire selenoprotein phospholipid hydroperoxide glutathione peroxidase (PHGPx Eq. 15-58, Table 15-4) has a high activity in the testis and in spermatids. However, in mature spermatozoa it forms an enzymatically inactive oxidatively crosslinked capsular material around the midpiece of the cell perhaps providing mechanical stability.268 A similar 34-kDa selenoprotein is present in sperm nuclei and may be essential for condensation of DNA.269 Sperm tails contain specialized cytoskele-tal proteins which form "outer dense fibers."270 In contrast to mammalian spermatozoa, nematode sperm move by ameboid motility that depends upon a specialized actin-like molecule.271 Sperm cells are unusually rich in polyamines, most of which are bound to RNA and DNA (Chapter 24). 

R. Prabhakar, T. Vreven, M. J. Frisch, K. Morokuma and D. G. Musaev, Is the protein surrounding the active site critical for hydrogen peroxide reduction by selenoprotein glutathione peroxidase An ONIOM study, J. Phys. Chem. B, 110 (2006) 13608-13613. 

Selenium This metal is an essential trace element that functions as a component of enzymes involved in antioxidant protection and thyroid hormone metabolism. The existence of a number of selenoproteins has been demonstrated. In several intra- and extracellular glutathione peroxidases and iodothyronine... 

K. T. Suzuki, K. Ishiwata, Y. Ogra, Incorporation of selenium into selenoprotein P and extracellular glutathione peroxidase HPLC-ICPMS data with enriched selenite, Analyst, 124 (1999), 1749D1753. 

Peroxynitrite reacts rapidly with glutathione peroxidase and other seleno compounds [(B23), see Table 6], A protective role of selenoproteins against peroxynitrite has been proposed, as glutathione proxidase in the presence of glutathione... 

Actually, glutathione peroxidase protects fromperoxynitrite-mediated oxidation and nitration reactions in model systems. Selenoprotein P from human plasma exhibits a similar property (A16, A17). A similar function of peroxynitritase has been ascribed to bacterial catalase/peroxidase (W10). 

Sies, H., Sharov, V. S., Klotz, L. O., and Briviba, K., Glutathione peroxidase protects against peroxynitrite-mediated oxidations. A new function for selenoproteins as peroxynitrite reductase. J. Biol Chem. 272, 27812-27817 (1997). 

Plasma from mammalia contains a selenoprotein that carries more than 50% of the selenium present. In rat, about 8% of the total selenium content is associated with this protein, selenoprotein P. A change in the selenium status of the rat leads to a rapid change of the selenium level attached to selenoprotein P, preferential to changes of other selenoproteins such as plasma glutathione peroxidase. ... 

Selenium is an issue in the biology of one of the poxviruses, one of the largest viruses in existence, as well as in the biology of coxsackievirus, one of the smallest of viruses. In the case of MCV, a poxvirus, the virus s genome codes for the well-known selenoprotein glutathione peroxidase. Apparently, this enzyme protects the virus from the defense system of the host. In the case of coxsackievirus, selenium deficiency in the host, whether a mouse or human, provokes activation of the virus within the host cell, resulting in disease to the host (damage to the heart). 

Synergistic interactions occur in other tissues and can have important biological and clinical consequences. For example, die interaction between selenium and iodine has been investigated.It is known that deiodinases are selenoproteins and that they remove iodine from T4 to produce the biologically active T3. Also the selenoprotein glutathione peroxidase is active in the thyroid in the destruction of excess hydrogen peroxide and is therefore important in thyroid hormone production. In certain areas of the world, combined selenium and iodine deficiency can occur and affect treatment provision of selenium maybe necessary to correct hypothyroidism, but also may precipitate its onset. 

The concentrations of selenium in whole blood and in plasma and/or serum are related to dietary intake. About 50% to 60% of the total plasma selenium is present as the protein selenoprotein P, a highly basic protein having multiple histidine residues and about 10 atoms of selenium per molecule, Around 30% of plasma selenium is present as glutathione peroxidase (GSHPx-3) and the remainder is incorporated into albumin as selenomethionine. ... 

Selenoprotein W. This is a selenoprotein found in skeletal muscle that is reduced in concentration in white muscle disease in animals. Deficiencies in the production of these selenoproteins, especially the glutathione peroxidases, are likely to be related to signs and symptoms of selenium deficiency disease. 

Early animal studies and human population surveys used whole blood as the main indicator of selenium status. Whole blood selenium can be determined after acid digestion using a fluorometric method. The more convenient carbon furnace atomic absorption spectroscopy (CFAAS) assay for plasma and/or serum selenium is now the most widely used procedure. The main components of plasma selenium are extracellular glutathione peroxidase (GSHPx 3) and selenoprotein P. 

Selenium, as selenocysteine, is incorporated into glutathione peroxidase (antioxidant), iodothyronine deiodinase (thyroid hormone regulation), and selenoprotein P (vitamin C metabolism). Prematurity, acute illness, chronic GI losses, and long-term selenium-free parenteral nutrition are associated with low serum selenium concentrations and decreased glutathione peroxidase activity. " The... 

As a component of glutathione peroxidase and the iodothyronine 5 -deiodinases, selenium is an essential micronutrient for humans. Its role in the deiodinase enzymes may be one reason that children require more selenium for growth than adults. Selenium is also a component of the enzyme thioredoxin reductase, which catalyses the NADPH-dependent reduction of the redox protein thioredoxin. Other selenium-containing proteins of unknown functions, including selenoprotein P found in the plasma, have also been identified. Excess selenium administered as selenite and selenate has been shown to be metabolized to methylated compounds and excreted. 

Hagmar L, Persson-Moschos M, Akesson B, et al. 1998. Plasma levels of selenium, selenoprotein P and glutathione peroxidase and their correlations to fish intake and serum levels of thyrotropin and thyroid hormones A study on Latvian fish consumers. Eur J Clin Nutr 52 796-800. 

Huang W, Akesson B, Svensson BG. 1995. Selenoprotein P and glutathione peroxidase (EC 1.11.1.9) in plasma as indices of selenium status in relation to the intake of fish. Br J Nutr 73 455-461. 

Fu L-H, Wang X-F, Eyal Y, She Y-M, Donald LJ, Standing KG and Ben-Hayyim G (2002) A selenoprotein in the plant kingdom mass spectrometry conforms that opal codon (UGA) encodes seleno-cysteine in Ghlamydomonas reingardtii glutathione peroxidase. J Biol Chem 277 25983-25991. 

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