Department of Microbiology, University of Illinois, Urbana, IL 61801.
Department of Microbiology, University of Illinois, Urbana, IL 61801
Proc Natl Acad Sci U S A. 2017 Aug 15;114(33):E6922-E6931. doi: 10.1073/pnas.1701587114. Epub 2017 Jul 10.
Microbial cytochrome peroxidases (Ccp) have been studied for 75 years, but their physiological roles are unclear. Ccps are located in the periplasms of bacteria and the mitochondrial intermembrane spaces of fungi. In this study, Ccp is demonstrated to be a significant degrader of hydrogen peroxide in anoxic Intriguingly, transcription requires both the presence of HO and the absence of O Experiments show that Ccp lacks enough activity to shield the cytoplasm from exogenous HO However, it receives electrons from the quinone pool, and its flux rate approximates flow to other anaerobic electron acceptors. Indeed, Ccp enabled to grow on a nonfermentable carbon source when HO was supplied. behaved similarly. This role rationalizes repression in oxic environments. We speculate that micromolar HO is created both biologically and abiotically at natural oxic/anoxic interfaces. The OxyR response appears to exploit this HO as a terminal oxidant while simultaneously defending the cell against its toxicity.
微生物细胞色素 c 过氧化物酶（Ccp）已经研究了 75 年，但它们的生理作用尚不清楚。Ccps 位于细菌的周质和真菌的线粒体膜间隙中。在这项研究中，Ccp 被证明是缺氧条件下过氧化氢的重要降解物。有趣的是，转录既需要 HO 的存在，也需要 O 的不存在。实验表明，Ccp 缺乏足够的活性来保护细胞质免受外源性 HO 的侵害。然而，它从醌库接收电子，其流动速率接近其他厌氧电子受体。事实上，当提供 HO 时，Ccp 使能够在非发酵碳源上生长。类似地，也表现出相同的行为。这种作用使在好氧环境中的阻遏合理化。我们推测，在生物和非生物的自然好氧/缺氧界面都可以产生毫摩尔级的 HO。OxyR 反应似乎利用这种 HO 作为末端氧化剂，同时防止细胞受到其毒性的影响。
