Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany.
Amino Acids. 2013 Feb;44(2):683-700. doi: 10.1007/s00726-012-1392-x. Epub 2012 Sep 15.
Mitochondria are tightly linked to cellular nutrient sensing, and provide not only energy, but also intermediates for the de novo synthesis of cellular compounds including amino acids. Mitochondrial metabolic enzymes as generators and/or targets of signals are therefore important players in the distribution of intermediates between catabolic and anabolic pathways. The highly regulated 2-oxoglutarate dehydrogenase complex (OGDHC) participates in glucose oxidation via the tricarboxylic acid cycle. It occupies an amphibolic branch point in the cycle, where the energy-producing reaction of the 2-oxoglutarate degradation competes with glutamate (Glu) synthesis via nitrogen incorporation into 2-oxoglutarate. To characterize the specific impact of the OGDHC inhibition on amino acid metabolism in both plant and animal mitochondria, a synthetic analog of 2-oxoglutarate, namely succinyl phosphonate (SP), was applied to living systems from different kingdoms, both in situ and in vivo. Using a high-throughput mass spectrometry-based approach, we showed that organisms possessing OGDHC respond to SP by significantly changing their amino acid pools. By contrast, cyanobacteria which lack OGDHC do not show perturbations in amino acids following SP treatment. Increases in Glu, 4-aminobutyrate and alanine represent the most universal change accompanying the 2-oxoglutarate accumulation upon OGDHC inhibition. Other amino acids were affected in a species-specific manner, suggesting specific metabolic rearrangements and substrate availability mediating secondary changes. Strong perturbation in the relative abundance of amino acids due to the OGDHC inhibition was accompanied by decreased protein content. Our results provide specific evidence of a considerable role of OGDHC in amino acid metabolism.
线粒体与细胞营养感应密切相关，不仅提供能量，还为包括氨基酸在内的细胞化合物的从头合成提供中间产物。因此，作为信号生成者和/或靶标的线粒体代谢酶是代谢物在分解代谢和合成代谢途径之间分配的重要参与者。高度调控的 2-氧戊二酸脱氢酶复合物（OGDHC）通过三羧酸循环参与葡萄糖氧化。它占据了循环中的一个兼性分支点，其中 2-氧戊二酸降解的产能反应与通过氮掺入 2-氧戊二酸生成谷氨酸（Glu）的反应竞争。为了表征 OGDHC 抑制对植物和动物线粒体中氨基酸代谢的具体影响，应用了 2-氧戊二酸的合成类似物琥珀酰膦酸（SP），对来自不同王国的活体系统进行了原位和体内研究。使用高通量基于质谱的方法，我们表明具有 OGDHC 的生物体通过显著改变其氨基酸池来响应 SP。相比之下，缺乏 OGDHC 的蓝藻在 SP 处理后氨基酸没有受到干扰。伴随 OGDHC 抑制的 2-氧戊二酸积累，Glu、4-氨基丁酸和丙氨酸的增加是最普遍的变化。其他氨基酸以物种特异性的方式受到影响，表明存在特定的代谢重排和介导次级变化的底物可用性。由于 OGDHC 抑制导致的氨基酸相对丰度的强烈扰动伴随着蛋白质含量的降低。我们的结果提供了 OGDHC 在氨基酸代谢中起重要作用的具体证据。
