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Selenium (Se) is well known to be essential for cell culture when using a serum-free medium, but not when a medium containing serum is used. This finding suggests that serum contains some usable formof Se. To identify the Se-supplier, T-lymphoma (Jurkat) cells were cultured for 3 days in the presence of human serum immunodepleted of Se-containing serum protein, selenoprotein Por extracellular glutathione peroxidase. | Eur. J. Biochem. 269 5746-5751 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.03298.x Characterization of selenoprotein P as a selenium supply protein Yoshiro Saito and Kazuhiko Takahashi Department of Hygienic Chemistry Graduate School of Pharmaceutical Sciences Hokkaido University Sapporo Japan Selenium Se is well known to be essential for cell culture when using a serum-free medium but not when a medium containing serum is used. This finding suggests that serum contains some usable form of Se. To identify the Se-supplier T-lymphoma Jurkat cells were cultured for 3 days in the presence of human serum immunodepleted of Se-containing serum protein selenoprotein P or extracellular g uaitìió i e peroxidase. The Se-dependent enzyme activities glutathione peroxidases and thioredoxin reductase and Se content within the cells markedly decreased only when cultured with selenoprotein P-depleted serum. Compared with other Se-containing proteins the addition of purified selenoprotein Pto the selenoprotein P-depleted serum or a serum-free medium was the most effective for the recovery of cellular glutathione peroxidase activity index of Se status . These results suggest that selenoprotein Pfunctions as a Se-supply protein delivering Se to the cells. Keywords selenium selenoprotein glutathione peroxidase. Se is an essential micronutrient and is incorporated into proteins in the form of selenocysteine Sec and selenomethionine. The term selenoprotein is restricted to Sec-containing proteins 1 and is to be distinguished from proteins that nonspecifically incorporate selenomethionine. Sec is encoded by a UGA codon formerly known only as a stop codon in the open reading frame of selenoprotein mRNA that is accompanied by a Sec insertion sequence element in the 3 -untranslated region in eukaryotes 2 . More than 15 selenoproteins have been found in animals and some of them have been shown to exert biological functions 3 . Four types of glutathione peroxidase GPx 4-7 three types of .
