Histidine is a source of the antioxidant, α-ketoglutarate, in Pseudomonas fluorescens challenged by oxidative stress
Histidine is a source of the antioxidant, α-ketoglutarate, in Pseudomonas fluorescens challenged by oxidative stress
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DOI：
10.1111/j.1574-6968.2010.02034.x
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发表时间：
2010-08-01
影响因子：
2.1
通讯作者：
Appanna, Vasu D.
中科院分区：
文献类型：
--
作者：
Lemire, Joseph;Milandu, Yves;Appanna, Vasu D.
α -酮戊二酸（KG）在活性氧（ROS）解毒中的作用直到最近才开始得到重视。这种酮酸以与nadph无关的方式中和ROS，同时形成琥珀酸盐和二氧化碳。为了进一步探讨KG在生命系统中的这一有趣属性，我们评估了组氨酸代谢在模式生物荧光假单胞菌（Pseudomonas fluorescens）受过氧化氢（H2O2）挑战时的意义。在这里，我们表明这种氨基酸确实有助于KG稳态，并且似乎是在氧化应激期间专门用于KG的产生。尽管介导三羧酸循环和氧化磷酸化的许多酶的活性急剧下降，但在应激细胞中，NAD-和nadp依赖性谷氨酸脱氢酶均上调。异柠檬酸脱氢酶- nad依赖性酶、琥珀酸脱氢酶、α -酮戊二酸脱氢酶、复合体I和复合体IV等酶在H2O2存在下生长时受到严重影响。氟柠檬酸盐（一种有效的柠檬酸代谢抑制剂）的研究清楚地表明，组氨酸在h2o2激发的细胞中优先用于KG的产生。调控实验也证实了H2O2胁迫诱导的代谢重编程导致的KG产量增加。这些数据进一步证实了KG在抗氧化防御中所起的关键作用。
The role of alpha-ketoglutarate (KG) in the detoxification of reactive oxygen species (ROS) has only recently begun to be appreciated. This ketoacid neutralizes ROS in an NADPH-independent manner with the concomitant formation of succinate and CO2. To further probe this intriguing attribute of KG in living systems, we have evaluated the significance of histidine metabolism in the model organism, Pseudomonas fluorescens, challenged by hydrogen peroxide (H2O2). Here, we show that this amino acid does contribute to KG homeostasis and appears to be earmarked for the production of KG during oxidative stress. Both the NAD- and the NADP-dependent glutamate dehydrogenases were upregulated in the stressed cells despite the sharp decline in the activities of numerous enzymes mediating the tricarboxylic acid cycle and oxidative phosphorylation. Enzymes such as isocitrate dehydrogenase-NAD dependent, succinate dehydrogenase, alpha-ketoglutarate dehydrogenase, Complex I, and Complex IV were severely affected in the P. fluorescens grown in the presence of H2O2. Studies with fluorocitrate, a potent inhibitor of citrate metabolism, clearly revealed that histidine was preferentially utilized in the production of KG in the H2O2-challenged cells. Regulation experiments also helped confirm that the metabolic reprogramming, resulting in the enhanced production of KG was induced by H2O2 stress. These data further establish the pivotal role that KG plays in antioxidative defense.