Abundance and tissue distribution of selenocysteine-containing proteins in the rat |
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Authors: | W C Hawkes E C Wilhelmsen A L Tappel |
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Affiliation: | Department of Food Science and Technology, University of California USA |
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Abstract: | The form and distribution of selenium (Se) in proteins from selected tissues of the rat were studied by measuring 75Se radioactivity in animals provided for 5 months with [75Se]selenite as the main dietary source of Se. Equilibration of the animals to a constant specific activity of 75Se allowed the measurement of 75Se to be used as a specific elemental assay for Se. Skeletal muscle, liver and blood accounted for 73% of the whole-body Se and 95% of the total Se-dependent glutathione peroxidase activity. Over 80% of the whole-body Se was in protein in the form of the selenoamino acid, selenocysteine. All other forms of Se that were measured accounted for less than 3% of the whole-body Se. The Se in protein was distributed in seven subunit sizes and nine chromatographic forms. The Se in glutathione peroxidase accounted for one-third of the whole-body Se. These results show that the main use of dietary Se, as selenite, in rats is for the synthesis of selenocysteine-containing proteins. Furthermore, the presence of two-thirds of the whole-body Se in nonglutathione peroxidase, selenocysteine-containing proteins suggests that there may be other important mammalian selenoenzymes besides glutathione peroxidase. |
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Keywords: | Address reprint requests to: Professor A. L. Tappel Department of Food Science and Technology 1480 Chemistry Annex University of California Davis CA 95616 USA |
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