[Progress in the study of mammalian selenoprotein]

Selenium is an essential trace element for animals and humans. Selenium exerts its biological function largely through selenoproteins. Up to now nine selenoproteins' cDNAs have been cloned and sequenced, which are cellular glutathione peroxidase (cGPX), extracellular glutathine peroxidase(eGPX), phospholipid hydroperoxidase glutathione peroxidase(PHGPX), gastrointestinal glutathione peroxidase (GPX-GI), type I iodothyronine 5'-deiodinase (ID I), type 2 iodothyronine 5'-deiodinase(ID II), type III iodothyronine 5-deiodinase(ID III), selenoprotein P (Se-P) and selenoprotein W. In all these selenoproteins Se is incorporated into the protein molecule via the selenocysteinyl-tRNA which recognizes the specific UGA codons in mRNA to insert selenocysteine into the primary structure of selenoproteins.