Kinetic evidence for rapid oxidation of (–)-epicatechin by human myeloperoxidase

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• 作者：Holger Spalteholz ; Paul Georg Furtmü ; ller ; Christa Jakopitsch ; Christian Obinger ; Tankred Schewe ; Helmut Sies ; Jü ; rgen Arnhold
• 关键词：Myeloperoxidase ; Epicatechin ; Compound I ; Compound II ; Transient-state kinetics
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2008
• 期刊代码：159_0006291x
• 类别：bio
• 出版时间：11 July 2008
• 卷：371
• 期：4
• 页码：810-813
• 文件大小：266 K

摘要

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 × 10⁷ and 4.5 × 10⁶ M⁻¹ s⁻¹, respectively (pH 7, 25 °C). The data indicate that (–)-epicatechin is capable of undergoing fast MPO-mediated one-electron oxidation.