The production of activated oxygen species by an interaction of methemoglobin with ascorbate |
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Authors: | U Benatti A Morelli L Guida A De Flora |
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Affiliation: | Institute of Biochemistry, School of Medicine, University of Genoa, Viale Benedetto XV/1, 16132 Genoa, Italy |
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Abstract: | Ascorbate reacts with methemoglobin to produce reactive oxygen species, most probably hydroxyl radicals. The main features of this system are: a) disappearance of ascorbate; b) consumption of oxygen with an ascorbate/O2 stoichiometry of 2:1; c) requirement of unliganded heme iron; d) formation of H2O2. The proposed mechanism involves an ascorbate-mediated interconversion of methemoglobin and oxy-hemoglobin, resulting in the production of H2O2. This product is decomposed by hemoglobin to produce hydroxyl radicals according to a Fenton-like reaction in which ascorbate recycles methemoglobin to hemoglobin. Alternative pathways of formation and of decomposition of H2O2 in this system appear to play a minor role. |
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Keywords: | MetHb fully oxidized tetrameric hemoglobin A Hb reduced tetrameric hemoglobin A PBS 20 mM Na phosphate pH 7.4 containing 146 mM NaCl (ref. 5) |
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