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

Alejandro K. Samhan-Arias, Rui O. Duarte, Francisco Javier Martín-Romero, José J. G. Moura, Carlos Gutiérrez-Merino

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)243-254
Number of pages12
JournalArchives of Biochemistry and Biophysics
Issue number2
Publication statusPublished - 15 Jan 2008


  • Ascorbate
  • Ascorbate free radical
  • Coenzyme Q
  • Cytochrome c
  • NADH oxidase
  • Synaptic plasma membranes


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