Redox activation of mitochondrial intermembrane space Cu,Zn-superoxide dismutase
Redox activation of mitochondrial intermembrane space Cu,Zn-superoxide dismutase
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DOI：
10.1042/bj20041683
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发表时间：
2005-04-01
影响因子：
4.1
通讯作者：
Cadenas, E
中科院分区：
文献类型：
--
作者：
Iñarrea, P;Moini, H;Cadenas, E
铜锌超氧化物歧化酶在线粒体膜间间隙的定位表明，超氧阴离子(O-2(.-))释放到线粒体膜间隙可能与超氧阴离子有关。本研究旨在检测铜锌超氧化物歧化酶的功能，并阐明其在膜间隙激活的分子基础。完整的大鼠肝脏线粒体既不清除也不突变外部产生的O-2(.-)，除非线粒体外膜被洋地黄选择性地破坏。蛋白质二硫化物异构酶的抑制剂杆菌肽在很大程度上抑制了线粒体外膜破坏后膜间隙铜锌超氧化物歧化酶的激活。硫醇烷化剂，如N-甲基马来酰亚胺或碘代乙酰胺，在外膜破裂期间但不会降低膜间隙铜，锌-超氧化物歧化酶的激活。这种抑制作用是通过将线粒体暴露在低微摩尔浓度的过氧化氢中，然后在烷化剂存在下破坏外膜来克服的。此外，单独的过氧化氢处理使完整的线粒体能够清除外部产生的O-2(.-)。这些发现表明，膜间隙铜锌超氧化物歧化酶在完整的线粒体中是无效的，其关键的硫醇基团的氧化修饰是其激活所必需的。
The localization of Cu,Zn-superoxide dismutase in the mitochondrial intermembrane space suggests a functional relationship with superoxide anion (O-2(.-)) released into this compartment. The present study was aimed at examining the functionality of Cu,Zn-superoxide dismutase and elucidating the molecular basis for its activation in the intermembrane space. Intact rat liver mitochondria neither scavenged nor dismutated externally generated O-2(.-), unless the mitochondrial outer membrane was disrupted selectively by digitonin. The activation of the intermembrane space Cu,Zn-superoxide dismutase following the disruption of mitochondrial outer membrane was largely inhibited by bacitracin, an inhibitor of protein disulphide-isomerase. Thiol alkylating agents, such as N-methylmaleimide or iocloacetamide, decreased intermembrane space Cu,Zn-superoxide dismutase activation during, but not after, disruption of the outer membrane. This inhibitory effect was overcome by exposing mitochondria to low micromolar concentrations of H2O2 before disruption of the outer membrane in the presence of the alkylating agents. Moreover, H2O2 treatment alone enabled intact mitochondria to scavenge externally generated O-2(.-). These findings suggest that intermembrane space Cu,Zn-superoxide dismutase is inactive in intact mitochondria and that an oxidative modification of its critical thiol groups is necessary for its activation.