title: Reduction of ascorbate free radical by the plasma membrane of synaptic terminals from rat brain.
abstract: 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of Extremadura, 06071 Badajoz, Spain.
authors.forename: Alejandro K
authors.initials: AK
authors.lastname: Samhan-Arias
authors.forename: Rui O
authors.initials: RO
authors.lastname: Duarte
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Martín-Romero
authors.forename: Jose J G
authors.initials: JJ
authors.lastname: Moura
authors.forename: Carlos
authors.initials: C
authors.lastname: Gutiérrez-Merino
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D001671:Biochemistry / Q000379:methods*; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D004492:Edetic Acid / Q000737:chemistry; D005609:Free Radicals; D019255:NADPH Oxidases / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D013569:Synapses / Q000378:metabolism*; D014451:Ubiquinone / Q000737:chemistry
chemical_list: D005609:Free Radicals; D014451:Ubiquinone; D045304:Cytochromes c; D004492:Edetic Acid; D019255:NADPH Oxidases; C025203:Ubiquinone Q1; D001205:Ascorbic Acid