title: The production of activated oxygen species by an interaction of methemoglobin with ascorbate.
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.
mesh_terms: D001205:Ascorbic Acid; D055598:Chemical Phenomena; D002621:Chemistry; D005609:Free Radicals; D006861:Hydrogen Peroxide; D006878:Hydroxides; D017665:Hydroxyl Radical; D008706:Methemoglobin; D010101:Oxygen Consumption
chemical_list: D005609:Free Radicals; D006878:Hydroxides; D017665:Hydroxyl Radical; D008706:Methemoglobin; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid