American Journal of Clinical Nutrition, Vol 27, 960-965, Copyright © 1974 by The American Society for Clinical Nutrition, Inc.

Selenium-glutathione peroxidase and vitamin E

¹ From the Department of Food Science and Technology, University of California, Davis, California 95616

Considerable data on vitamin E cannot be reconciled with the simple concept that lipid peroxidation in vivo is inhibited solely by the chain-breaking reactions of vitamin E. Developing knowledge of the selenium-glutathione (Se-GSH) peroxidase system provides more detailed understanding of how this system links with vitamin E reactions. In many tissues, GSH peroxidase has high specific activity, and may be a major system that can utilize GSH. Comparison of partially purified liver and lung GSH peroxidase with the blood enzyme studied by L. Flohé et al. and C. Little et al. shows that all three are characterized by 1) specificity for reduction of a hydroperoxide with little effect of the neighboring alkyl or aryl group, and 2) specificity for glutathione as a reductant. The University of Wisconsin group (7, 13) has made major advances showing that Se is contained in purified GSH peroxidase, and that GSH peroxidase activity in some rat tissues correlates with dietary Se. In our laboratory, rats fed Se-deficient diets supplemented with 0, 0.05, 0.2, or 2.0 ppm Se methionine had GSH peroxidase activity proportional to the log of the concentration of dietary Se. The increase of GSH peroxidase activity with dietary Se supplementation was greatest in plasma, with other tissues following in the order liver > heart > kidney > erythrocytes lung > muscle. Also, six tissues of rats fed a Se-deficient diet showed decreases of GSH peroxidase activity during a 4-week depletion period. After 2 weeks of depletion, repletion with 2 ppm Se methionine resulted in a corresponding increase of GSH peroxidase activity. Ten tissues of chicks fed a basal Se-deficient diet supplemented with either 0 to 14 ppm Se methionine in 10 increments or with 0 to 0.14 ppm selenite in 5 increments showed corresponding increases in GSH peroxidase activities. Interactions were tested in systems that contained arachidonic acid and cell cytosol from various rat and chicken tissues. Peroxidation inhibition was related to GSH peroxidase activity and the concentration of added GSH. The stimulation of added peroxide was likewise inhibited as a function of GSH peroxidase and GSH.

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