title: Kinetic evidence for rapid oxidation of (-)-epicatechin by human myeloperoxidase.
abstract: Apocynin has been reported to require dimerization by myeloperoxidase (MPO) to inhibit leukocyte NADPH oxidase. (-)-Epicatechin, a dietary flavan-3-ol, has been identified as a 'prodrug' of apocynin-like metabolites that inhibit endothelial NADPH oxidase activity and elevate the cellular level of nitric oxide. Since (-)-epicatechin has tentatively been identified as substrate of MPO, we studied the one-electron oxidation of (-)-epicatechin by MPO. By using multi-mixing stopped-flow technique, we demonstrate that (-)-epicatechin is one of the most efficient electron donors for heme peroxidases investigated so far. Second order rate constants for the (-)-epicatechin-mediated conversion of MPO-compound I to compound II and compound II to resting enzyme were estimated to be 1.9 x 10(7) and 4.5 x 10(6) M(-1)s(-1), respectively (pH 7, 25 degrees C). The data indicate that (-)-epicatechin is capable of undergoing fast MPO-mediated one-electron oxidation.
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, D-04107 Leipzig, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Spalteholz
authors.forename: Paul Georg
authors.initials: PG
authors.lastname: Furtmüller
authors.forename: Christa
authors.initials: C
authors.lastname: Jakopitsch
authors.forename: Christian
authors.initials: C
authors.lastname: Obinger
authors.forename: Tankred
authors.initials: T
authors.lastname: Schewe
authors.forename: Helmut
authors.initials: H
authors.lastname: Sies
authors.forename: Jürgen
authors.initials: J
authors.lastname: Arnhold
mesh_terms: D002392:Catechin / Q000737:chemistry*; D004583:Electrons; D006801:Humans; D007700:Kinetics; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry*
chemical_list: D002392:Catechin; D009195:Peroxidase