Semidehydroascorbate reductase

FIGURE 29.1 Pathways of the chain-breaking action of vitamin E in lipid peroxidation and its subsequent regeneration. LOOH lipid hydroperoxide, LOO lipid peroxyl radical, vitamin C ascorbate radical (semi-dehydroascorbate), vitamin E a-tocopheroxyl radical. The lipid peroxyl radical is reduced to lipid hydroperoxide by tocopherol. The resulting tocopheroxyl radical can be re-reduced by ascorbate. The thus formed ascorbate radical can be reduced to ascorbate by the NADH-dependent semidehydroascorbate reductase. 

Diliberto E) Ir, Dean G, Carter C, and Allen PL (1982) Tissue, subcellular, and submito-chondrial distributions of semidehydroascorbate reductase possible role of semide-hydroascorbate reductase in cofactor regeneration. Journal of Neurochemistry 39, 563-8. 

Both the above hydroxylations seem to involve the recycling of tetrahydrobiopterin which may require ascorbic acid. Recently it has been suggested that dopamine-jS-hydroxylase (DBH) works in tandem with semidehydroascorbate reductase (SDR) in order to recycle the vitamin and oxidise NADHj as in Figure 5.15. 

Khatami, M., Rod, L. E., Li, W., and Rockey, J. H., 1986, Ascorbic acid regeneration in bovine ocular tissues by NADPH-dependent semidehydroascorbic acid reductase, Exp. Eye Res. 43 167-175. 

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