Ascorbate radical biochemical reactions

The biochemical reactions of ascorbic acid as a synergist with vitamin E and as a known aqueous free radical scavenger are probably the basis of the known relationship of ascorbic acid and vitamin E in protecting the lung against oxidants (Tappel, 1968). 

Ascorbic acid is a reasonably strong reducing agent. The biochemical and physiological functions of ascorbic acid most likely derive from its reducing properties—it functions as an electron carrier. Loss of one electron due to interactions with oxygen or metal ions leads to semidehydro-L-ascorbate, a reactive free radical (Figure 18.30) that can be reduced back to L-ascorbic acid by various enzymes in animals and plants. A characteristic reaction of ascorbic acid is its oxidation to dehydro-L-aseorbie add. Ascorbic acid and dehydroascor-bic acid form an effective redox system. 

Rowley, D.A. and Halliwell, B. (1983b). Superoxide-dependent and ascorbate-dependent formation of hydroxyl radicals in the presence of copper salts a physiologically significant reaction. Arch. Biochem. Biophys. 225, 279-284. 

Bisby, R.H. and Parker, A.W. 1995. Reaction of ascorbate with the a-tocopheroxyl radical in micellar and bilayer membrane systems. Arch. Biochem. Biophys. 317 170-178. 

Neta P, Eluie RE, Mosseri S, Shastri LV, Mittal JP, Maruthamuthu P, Steenken S (1989) Rate constants for reduction of substituted methylperoxyl radicals by ascorbate ions and N,N,N, Al -tetrameth-yl-p-phenylenediamine. J Phys Chem 93 4099-4104 Netto LES, Stadtman ER (1996) The iron-catalyzed oxidation of dithiothreitol is a biphasic process hyudrogen peroxide is involved in the initiation of a free-radical chain of reactions. Arch Biochem Biophys 333 233-242... 

Hiner ANP, Martmez JI, Amao MB et al (2001) Detection of a tryptophan radical in the reaction of ascorbate peroxidase with hydrogen peroxide. Eur J Biochem 268 3091-3098... 

Rowley DA, Halliwell B (1983) Superoxide-dependent and ascorbate-dependent formation of hydroxyl radicals in the presence of copper salts a physiologically significant reaction Arch Biochem Biophys 225 279-284 Saedi MS, Smith CG, Frampton J, Chambers I, Harrison PR, Sunde RA (1988) Effect of selenium status on mRNA levels for glutathione peroxidase in rat liver. Biochem Biophys Res Commun 153 855-861 Salnikow K, Zhitkovich A, Costa M (1992) Analysis of the binding sites of chromium to DNA and protein in vitro and in intact cells. Carcinogenesis 13 2341-2346... 

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