Reduction of ascorbate free radical by the plasma membrane of synaptic terminals from rat brain

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• 作者：Alej ; ro K. Samhan-Arias ; Rui O. Duarte ; Francisco Javier Martí ; n-Romero ; Jose J.G. Moura ; Carlos Gutié ; rrez-Merino
• 关键词：Ascorbate free radical ; Ascorbate ; Coenzyme Q ; Coenzyme Q₁ ; Synaptic plasma membranes ; NADH oxidase ; Cytochrome c
• 刊名：Archives of Biochemistry and Biophysics
• 出版年：2008
• 出版时间：15 January 2008
• 年：2008
• 卷：469
• 期：2
• 页码：243-254
• 全文大小：873 K

文摘

Synaptic plasma membranes (SPMV) decrease the steady state ascorbate free radical (AFR) concentration of 1 mM 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 μM. 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 Q₁ and cytochrome c can be accounted for by the increase of the AFR concentration generated by the redox pairs ascorbate/coenzyme Q₁ 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.