期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 103, 期 20, 页码 7607-7612出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0510977103
关键词
flavin; iron-sulfur cluster; semiquinone; oxidative stress
资金
- MRC [MC_U105663141] Funding Source: UKRI
- Medical Research Council [MC_U105663141] Funding Source: Medline
- Medical Research Council [MC_U105663141] Funding Source: researchfish
NADH:ubiquinone oxicloreductase (complex 1) is a major source of reactive oxygen species in mitochondria and a significant contributor to cellular oxidative stress. Here, we describe the kinetic and molecular mechanism of superoxide production by complex I isolated from bovine heart mitochondria and confirm that it produces predominantly superoxide, not hydrogen peroxide. Redox titrations and electron paramagnetic resonance spectroscopy exclude the iron-sulfur clusters and flavin radical as the source of superoxide, and, in the absence of a proton motive force, superoxide formation is not enhanced during turnover. Therefore, superoxide is formed by the transfer of one electron from fully reduced flavin to O-2. The resulting flavin radical is unstable, so the remaining electron is probably redistributed to the iron-sulfur centers. The rate of superoxide production is determined by a bimolecular reaction between O-2 and reduced flavin in an empty active site. The proportion of the flavin that is thus competent for reaction is set by a preecluilibrium, determined by the dissociation constants of NADH and NADI, and the reduction potentials of the flavin and NADI. Consequently, the ratio and concentrations of NADH and NADI determine the rate of superoxide formation. This result clearly links our mechanism for the isolated enzyme to studies on intact mitochondria, in which superoxide production is enhanced when the NADI pool is reduced. Therefore, our mechanism forms a foundation for formulating causative connections between complex I defects and pathological effects.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据