title: The metal-catalyzed oxidation of methionine in peptides by Fenton systems involves two consecutive one-electron oxidation processes.
abstract: The one-electron oxidation of methionine (Met) plays an important role in the redox reactions of Met in peptides and proteins under conditions of oxidative stress, e.g., during the metal-catalyzed oxidation of beta-amyloid peptide (beta A). However, little information is available with regard to mechanisms and product formation during the metal-catalyzed oxidation of Met. Here, we demonstrate that two-electron oxidation of Met in Fenton reactions, carried out aerobically by [Fe(II)(EDTA)](2-) and H(2)O(2) (EDTA = ethylenediaminetetra acetate) is the consequence of two consecutive one-electron transfer reactions carried out by either free or complexed hydroxyl radicals, followed by the reaction of an intermediary sulfur-nitrogen bonded radical cation (sulfuranyl radical) with O(2). The model peptide Met-Met represents an ideal substrate for these investigations as its one-electron oxidation, followed by reaction with molecular oxygen, produces unique intermediates, azasulfonium diastereomers, which can be chemically isolated before hydrolysis to sulfoxide occurs.
authors.affiliation: Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047-2504, USA.
authors.forename: J
authors.initials: J
authors.lastname: Hong
authors.forename: C
authors.initials: C
authors.lastname: Schöneich
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry; D001667:Binding, Competitive; D004151:Dipeptides / Q000737:chemistry; D004492:Edetic Acid / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D016166:Free Radical Scavengers; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D007930:Leucine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000737:chemistry*; D008715:Methionine / Q000737:chemistry*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010455:Peptides / Q000737:chemistry*; D013237:Stereoisomerism; D013440:Sulfides / Q000737:chemistry; D013454:Sulfoxides / Q000737:chemistry
chemical_list: D016229:Amyloid beta-Peptides; D004151:Dipeptides; D005296:Ferrous Compounds; D016166:Free Radical Scavengers; D008670:Metals; D010455:Peptides; D013440:Sulfides; D013454:Sulfoxides; D017665:Hydroxyl Radical; D004492:Edetic Acid; D008715:Methionine; D006861:Hydrogen Peroxide; D007930:Leucine