Reduction of ascorbate free radical by the plasma membrane of synaptic terminals from rat brain.
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.
Samhan-Arias
Alejandro K
AK
Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of Extremadura, 06071 Badajoz, Spain.
Duarte
Rui O
RO
Martín-Romero
Francisco Javier
FJ
Moura
Jose J G
JJ
Gutiérrez-Merino
Carlos
C
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
D005609:Free Radicals; D014451:Ubiquinone; D045304:Cytochromes c; D004492:Edetic Acid; D019255:NADPH Oxidases; C025203:Ubiquinone Q1; D001205:Ascorbic Acid