IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal.
Free Radic Biol Med. 2012 Jan 15;52(2):402-9. doi: 10.1016/j.freeradbiomed.2011.10.492. Epub 2011 Nov 4.
Mitochondria are a main providers of high levels of energy, but also a major source of reactive oxygen species (ROS) during normal oxidative metabolism. The involvement of Neurospora crassa alternative NAD(P)H dehydrogenases in mitochondrial ROS production was evaluated. The growth responses of a series of respiratory mutants to several stress conditions revealed that disrupting alternative dehydrogenases leads to an increased tolerance to the redox cycler paraquat, with a mutant devoid of the external NDE1 and NDE2 enzymes being significantly more resistant. The nde1nde2 mutant mitochondria show a significant decrease in ROS generation in the presence and absence of paraquat, regardless of the respiratory substrate used, and an intrinsic increase in catalase activity. Analysis of ROS production by a complex I mutant (nuo51) indicates that, as in other organisms, paraquat-derived ROS in Neurospora mitochondria occur mainly at the level of complex I. We propose that disruption of the external NAD(P)H dehydrogenases NDE1 and NDE2 leads to a synergistic effect diminishing ROS generation by the mitochondrial respiratory chain. This, in addition to a robust increase in scavenging capacity, provides the mutant strain with an improved ability to withstand paraquat treatment.
线粒体是高能的主要提供者，但在正常氧化代谢过程中也是活性氧（ROS）的主要来源。评估了粗糙脉孢菌替代 NAD（P）H 脱氢酶在线粒体 ROS 产生中的作用。一系列呼吸突变体对多种应激条件的生长反应表明，破坏替代脱氢酶会导致对氧化还原循环抑制剂百草枯的耐受性增加，缺乏外部 NDE1 和 NDE2 酶的突变体具有明显更高的抗性。nde1nde2 突变体线粒体在有无百草枯的情况下，无论使用何种呼吸底物，ROS 的产生都显著减少，过氧化氢酶活性也固有增加。对复合物 I 突变体（nuo51）的 ROS 产生分析表明，与其他生物体一样，Neurospora 线粒体中的百草枯衍生 ROS 主要发生在复合物 I 水平。我们提出，外部 NAD（P）H 脱氢酶 NDE1 和 NDE2 的破坏会导致协同作用，减少线粒体呼吸链产生的 ROS。除了清除能力的大幅增加外，这为突变菌株提供了更好的能力来耐受百草枯处理。
