Kinetic evidence for rapid oxidation of (-)-epicatechin by human myeloperoxidase.
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.
Spalteholz
Holger
H
Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, D-04107 Leipzig, Germany.
Furtmüller
Paul Georg
PG
Jakopitsch
Christa
C
Obinger
Christian
C
Schewe
Tankred
T
Sies
Helmut
H
Arnhold
Jürgen
J
D002392:Catechin / Q000737:chemistry*; D004583:Electrons; D006801:Humans; D007700:Kinetics; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry*
D002392:Catechin; D009195:Peroxidase