title: New insights into thiocyanate oxidation by human myeloperoxidase.
abstract: Human myeloperoxidase (MPO) uses chloride and thiocyanate as physiological substrates at neutral pH. Oxidation of thiocyanate to hypothiocyanite mediated by the redox intermediate Compound I rapidly restores the ferric state of MPO. At low thiocyanate concentration and in the presence of hydrogen peroxide the observed reaction sequence is Compound I→ferric MPO→Compound II→MPO-cyanide complex, whereas at high thiocyanate concentrations and in the absence of H2O2the only observed transition is Compound I→ferric MPO. The reaction of ferric MPO with hypothiocyanite directly forms the MPO-cyanide complex, whereas a transient product derived from the reaction between hypothiocyanite and hydrogen peroxide is demonstrated to mediate the conversion of ferric MPO to Compound II. Mechanisms for those reactions are discussed and proposed.
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany.
authors.forename: Denise
authors.initials: D
authors.lastname: Schlorke
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Flemmig
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Gau
authors.affiliation: Department of Chemistry, Division of Biochemistry, University of Natural Resources and Life Sciences, Vienna, Austria.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Furtmüller
authors.affiliation: Department of Chemistry, Division of Biochemistry, University of Natural Resources and Life Sciences, Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Obinger
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany. Electronic address: juergen.arnhold@medizin.uni-leipzig.de.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Arnhold
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry*; D012996:Solutions; D013861:Thiocyanates / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D012996:Solutions; D013861:Thiocyanates; D014867:Water; C014607:hypothiocyanite ion; D006861:Hydrogen Peroxide; D009195:Peroxidase; C031760:thiocyanate
keywords: Compound I; Compound II; Hypothiocyanite; Myeloperoxidase; Stopped flow spectroscopy; Thiocyanate