%0 Journal Article %J Arch Biochem Biophys %D 2008 %T Reduction of ascorbate free radical by the plasma membrane of synaptic terminals from rat brain %A Samhan-Arias, A. K. %A Duarte, R. O. %A Martin-Romero, F. J. %A Moura, J. J. %A Gutierrez-Merino, C. %K *Free Radicals %K Animals %K Ascorbic Acid/*metabolism %K Biochemistry/*methods %K Brain/*metabolism %K Cell Membrane/*metabolism %K Cytochromes c/metabolism %K Edetic Acid/chemistry %K NADPH Oxidase/metabolism %K Oxidation-Reduction %K Rats %K Synapses/*metabolism %K Ubiquinone/chemistry %M 17963686 %P 243-54 %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17963686 %V 469 %X

Synaptic plasma membranes (SPMV) decrease the steady state ascorbate free radical (AFR) concentration of 1mM ascorbate in phosphate/EDTA buffer (pH 7), due to AFR recycling by redox coupling between ascorbate and the ubiquinone content of these membranes. In the presence of NADH, but not NADPH, SPMV catalyse a rapid recycling of AFR which further lower the AFR concentration below 0.05 microM. These results correlate with the nearly 10-fold higher NADH oxidase over NADPH oxidase activity of SPMV. SPMV has NADH-dependent coenzyme Q reductase activity. In the presence of ascorbate the stimulation of the NADH oxidase activity of SPMV by coenzyme Q(1) and cytochrome c can be accounted for by the increase of the AFR concentration generated by the redox pairs ascorbate/coenzyme Q(1) and ascorbate/cytochrome c. The NADH:AFR reductase activity makes a major contribution to the NADH oxidase activity of SPMV and decreases the steady-state AFR concentration well below the micromolar concentration range.

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1096-0384 (Electronic)0003-9861 (Linking)Journal ArticleResearch Support, Non-U.S. Gov't

%8 Jan 15