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Role of Coenzyme Q and Superoxide in Vitamin E Cycling

  • Chapter
Fat-Soluble Vitamins

Part of the book series: Subcellular Biochemistry ((SCBI,volume 30))

Abstract

Coenzyme Q, an indispensable component of membrane electron transport chains, can also function, in its reduced form, as an antioxidant in membranes and lipoproteins. It decreases lipid peroxidation in liposomes, mitochondria, cells, and low-density lipoprottein (LDL), which explains its ubiquitous presence in biological systems, even where no energy transduction occurs (e.g., LDL). Electron transport reduces coenzyme Q to antioxidant forms, but it is unknown if it is reduced in the absence of electron transport. In an aprotic environment (dimethylsolfoxide, DMSO), in aqueous environments, and in liposomes, we found that Superoxide reduces coenzyme Q, and that this reduced coenzyme Q can, in turn, regenerate vitamin E from its radical form, thus “recycling” vitamin E. In HL-60 cells, coenzyme Q protected membrane phospholipids against peroxidation induced by a lipid-soluble azo-initiator of peroxyl radicals, 2,2′-azobis (2,4-dimethylvaleronitrile) (AMVN), only when Superoxide was generated in the incubation system. Thus, coenzyme Q is reduced by Superoxide, and the reduced forms of coenzyme Q exert antioxidant effects, either directly or via recycling of the vitamin E radical. Hence, under conditions of high Superoxide production (i.e., high oxidative stress), coenzyme Q’s antioxidant power is multiplied manifold by its continuous reduction by the very Superoxide which causes oxidative stress.

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Kagan, V.E., Tyurina, Y.Y., Witt, E. (1998). Role of Coenzyme Q and Superoxide in Vitamin E Cycling. In: Quinn, P.J., Kagan, V.E. (eds) Fat-Soluble Vitamins. Subcellular Biochemistry, vol 30. Springer, Boston, MA. https://doi.org/10.1007/978-1-4899-1789-8_20

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