SELEN A ORGANISMUS

Selenium and the Organism

Selenium is an essential trace element for animals. It is biologically active as selenocysteine in the active centreof selenoproteins with enzymatic functions. Incorporation of selenocysteine occurs on the basis of genetic expressionand selenium is the only trace element under direct genetic control. Selenocysteine can be considered the 21st aminoacid with regard to its biosynthesis and incorporation into proteins. At least two types of selenoproteins are necessaryfor each animal cell, the first from the family of GSH-peroxidases and the second from the family of deiodinases.GSH-peroxidases are the most powerful antioxidant enzymes, which defend the cell and whole organism againstoxidative damage and thus from oxidative diseases and disorders such as cardiovascular diseases, malignancies,bacterial or viral diseases, muscle dystrophy, arthropathy, arterial plaques, and others. GSH-Px have many otherregulatory functions such as regulation of biosynthesis of prostaglandins, prostacycline, leukotrienes, and thrombo-xans. Deiodinases regulate the metabolism of biologically active triiodothyronine and thus thyroid hormoneregulation of the whole organism. Selenoproteins act against cancerogenic effects of some organic molecules andbind heavy metals. Tissue-specific selenoproteins without a known biological function have been detectes in somespecialised tissues with a high priority for selenium. One of the regulators of selenoprotein synthesis is the seleniumstatus of the organism. Its state and intake may be assessed by analyses of selenium indexes. The most often usedindexes are serum selenium and urinary selenium. On the basis of its analyses in six regions of the Czech Republic,severe selenium deficiency has been found in inhabitants of this country, which is even profound for more distressedgroups like growing children, pregnant and lactating women, and the elderly.

Key words:
selenium, selenoprotein, GSH-peroxidase, deiodinase, selenium deficiency in CR.