Inhibition of the alpha-ketoglutarate dehydrogenase-mediated reactive oxygen species generation by lipoic acid
Inhibition of the alpha-ketoglutarate dehydrogenase-mediated reactive oxygen species generation by lipoic acid
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DOI：
10.1111/j.1471-4159.2009.05942.x
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发表时间：
2009-05-01
影响因子：
4.7
通讯作者：
Adam-Vizi, Vera
中科院分区：
文献类型：
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作者：
Ambrus, Attila;Tretter, Laszlo;Adam-Vizi, Vera
二氢硫辛酰胺脱氢酶（LADH）是一种黄素酶，作为α - 酮戊二酸脱氢酶复合物（α - KGDHC）的一个亚基。α - KGDHC产生活性氧（ROS）的过程被归因于LADH（E3亚基），并由E3的心肌黄酶活性所解释。α - KGDHC的功能障碍以及伴随的ROS产生与神经退行性变、缺血 - 再灌注以及其他病理状况有关。在这项工作中，我们深入研究了分离的LADH和α - KGDHC产生ROS的细节。我们发现α - KGDHC的E3亚基平行产生超氧化物和过氧化氢，而硫辛酸（LA）作用于E3亚基上游的位点可阻断这一过程。α - KGDHC在反向模式下（在高NADH/NAD⁺比值和低pH条件下）与病理相关的ROS产生也可被LA抑制。我们的结果与先前提出的LADH产生pH依赖性ROS的机制相矛盾，通过一种生理学相关的检测方法表明在酸性pH下E3功能性同型二聚体不会解聚。还表明LA可能有助于减少病理条件下与过量ROS产生相关的细胞损伤。
Dihydrolipoamide dehydrogenase (LADH) is a flavo-enzyme that serves as a subunit of alpha-ketoglutarate dehydrogenase complex (alpha-KGDHC). Reactive oxygen species (ROS) generation by alpha-KGDHC has been assigned to LADH (E3 subunit) and explained by the diaphorase activity of E3. Dysfunctions of alpha-KGDHC and concurrent ROS production have been implicated in neurodegeneration, ischemia-reperfusion, and other pathological conditions. In this work we investigated the in-depth details of ROS generation by isolated LADH and alpha-KGDHC. We found a parallel generation of superoxide and hydrogen peroxide by the E3 subunit of alpha-KGDHC which could be blocked by lipoic acid (LA) acting on a site upstream of the E3 subunit. The pathologically relevant ROS generation (at high NADH/NAD(+) ratio and low pH) in the reverse mode of alpha-KGDHC could also be inhibited by LA. Our results contradict the previously proposed mechanism for pH-dependent ROS generation by LADH, showing no disassembling of the E3 functional homodimer at acidic pH using a physiologically relevant method for the examination. It is also suggested that LA could be beneficial in reducing the cell damage related to excessive ROS generation under pathological conditions.