Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla Sevilla, Spain.
Front Plant Sci. 2013 Aug 19;4:310. doi: 10.3389/fpls.2013.00310. eCollection 2013.
Photosynthesis, the primary source of biomass and oxygen into the biosphere, involves the transport of electrons in the presence of oxygen and, therefore, chloroplasts constitute an important source of reactive oxygen species, including hydrogen peroxide. If accumulated at high level, hydrogen peroxide may exert a toxic effect; however, it is as well an important second messenger. In order to balance the toxic and signaling activities of hydrogen peroxide its level has to be tightly controlled. To this end, chloroplasts are equipped with different antioxidant systems such as 2-Cys peroxiredoxins (2-Cys Prxs), thiol-based peroxidases able to reduce hydrogen and organic peroxides. At high peroxide concentrations the peroxidase function of 2-Cys Prxs may become inactivated through a process of overoxidation. This inactivation has been proposed to explain the signaling function of hydrogen peroxide in eukaryotes, whereas in prokaryotes, the 2-Cys Prxs of which were considered to be insensitive to overoxidation, the signaling activity of hydrogen peroxide is less relevant. Here we discuss the current knowledge about the mechanisms controlling 2-Cys Prx overoxidation in chloroplasts, organelles with an important signaling function in plants. Given the prokaryotic origin of chloroplasts, we discuss the occurrence of 2-Cys Prx overoxidation in cyanobacteria with the aim of identifying similarities between chloroplasts and their ancestors regarding their response to hydrogen peroxide.
光合作用是生物界生物质和氧气的主要来源，涉及电子在氧气存在下的运输，因此，叶绿体是活性氧物种的重要来源，包括过氧化氢。如果过氧化氢积累到高水平，可能会产生毒性作用；然而，它也是一种重要的第二信使。为了平衡过氧化氢的毒性和信号转导活性，必须严格控制其水平。为此，叶绿体配备了不同的抗氧化系统，如 2-Cys 过氧化物酶（2-Cys Prxs），能够还原氢和有机过氧化物的基于硫醇的过氧化物酶。在高过氧化物浓度下，2-Cys Prxs 的过氧化物酶功能可能会通过过度氧化过程失活。这种失活被认为可以解释过氧化氢在真核生物中的信号转导功能，而在原核生物中，2-Cys Prxs 被认为对过度氧化不敏感，过氧化氢的信号转导活性相关性较低。在这里，我们讨论了关于控制叶绿体中 2-Cys Prx 过度氧化的机制的现有知识，叶绿体是植物中具有重要信号功能的细胞器。鉴于叶绿体的原核起源，我们讨论了蓝细菌中 2-Cys Prx 过度氧化的发生，目的是确定叶绿体与其祖先在对过氧化氢的反应方面的相似性。
