Incorporation of selenium from selenite and selenocystine into glutathione peroxidase in the isolated perfused rat liver |
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Authors: | Roger A Sunde William G Hoekstra |
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Institution: | Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, WI 53706 USA |
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Abstract: | The erythrocyte-free, isolated perfused rat liver was used to study the incorporation of selenium into glutathione peroxidase. Gel filtration and ion exchange chromatography of liver supernatant demonstrated 75Se incorporation into glutathione peroxidase. A 9-fold excess of unlabelled selenium as selenite or selenide very effectively reduced 75Se incorporation from L75Se]-selenocystine, but a 100-fold excess of unlabelled selenium as selenocystine was relatively ineffective as compared to selenite or selenide in diluting 75Se incorporation from 75Se]selenite. These results indicate that selenide and selenite are more readily metabolized than is selenocysteine to the immediate selenium precursor used for glutathione peroxidase synthesis, and suggest a posttranslational modification at another amino acid residue, rather than direct incorporation of selenocysteine, as the mechanism for formation of the presumed selenocysteine moiety of the enzyme. |
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