title: The ascorbate: ascorbate free radical oxidoreductase from the erythrocyte membrane is not cytochrome b561.
abstract: Erythrocytes contain a plasma membrane redox system that can reduce extracellular ascorbate radicals by using intracellular ascorbate as an electron donor. In this study, the hypothesis was tested that cytochrome b561 was a component of this system. Spectroscopic analysis of erythrocyte membrane preparations revealed the presence of cytochrome b5 and hemoglobin but also of a cytochrome with properties similar to cytochrome b561, reducible by ascorbate and insensitive to CO. The presence of cytochrome b561 was studied further by reverse transcriptase-PCR analysis of erythrocyte progenitor cells, reticulocytes. However, no cytochrome b561 mRNA could be found. These results were corroborated by Western blot analysis with an anti-cytochrome b561 serum. No cytochrome b561 protein could be detected in extracts of erythrocyte membranes. It is therefore concluded that erythrocytes do not contain cytochrome b561 in their membranes. The possible involvement of other b-cytochromes in ascorbate-ascorbate free radical oxidoreductase activity is discussed.
authors.affiliation: Sylvius Laboratory, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: M M
authors.initials: MM
authors.lastname: Van Duijn
authors.forename: J T
authors.initials: JT
authors.lastname: Buijs
authors.forename: J
authors.initials: J
authors.lastname: Van der Zee
authors.forename: P J
authors.initials: PJ
authors.lastname: Van den Broek
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism*; D002460:Cell Line; D003573:Cytochrome b Group / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000737:chemistry / Q000201:enzymology*; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013057:Spectrum Analysis
chemical_list: D003573:Cytochrome b Group; D005609:Free Radicals; C023646:cytochrome b561; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH); D001205:Ascorbic Acid