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Effects of Vitamin E Deficiency on the Activities of Lipid-Requiring Enzymes in Rabbit Liver and Muscle¹

Department of Biochemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 4, Thailand

The effects of vitamin E deficiency on membrane integrity were studied by examining the temperature dependence of membrane-bound enzyme activities in liver mitochondria and microsome and in muscle sarcoplasmic reticulum. In vitamin E-deficient rabbits, the specific activities at 37° of mitochondrial oligomycin-sensitive ATPase (EC 3.6.1.3), ß-hydroxybutyrate dehydrogenase (EC 1.1.1.30), and microsomal glucose-6-phosphatase (EC 3.1.3.9) were increased, whereas those of microsomal NADH cytochrome C reductase (EC 1.6.99.3) and sarcoplasmic reticulum Ca-ATPase were reduced in comparison to control rabbits. Arrhenius plots of activity against temperature yielded a linear plot over the range 10 to 40° in the case of ß-hydroxybutyrate dehydrogenase, NADH cytochrome C reductase and Ca-ATPase, and multiple discontinuities for glucose-6-phosphatase and oligomycin-sensitive ATPase. In control rabbits, all five enzymes showed a single discontinuity in the Arrhenius plot over the range 16 to 19°. These results reflect changes to the microenvironment of membrane-bound enzymes as a consequence of vitamin E depletion.

KEY WORDS: • membrane-bound enzyme • Arrhenius plot • vitamin E deficiency • rabbit

¹ Supported by grants from the National Research Council of Thailand and the Faculty of Graduate Studies, Mahidol University. Submitted by C.V. in partial fulfillment for the degree of Master of Science, Faculty of Science, Mahidol University. Presented in part at the Bangkok Symposium on Scientific Research, December 16 to 17, 1977.

² Requests for reprints should be directed to Dr. P. Komaratat, Department of Biochemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok, Thailand.

Manuscript received 13 July 1978.