Glycolytic enzymes associate dynamically with mitochondria in response to respiratory demand and support substrate channeling
Glycolytic enzymes associate dynamically with mitochondria in response to respiratory demand and support substrate channeling
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DOI：
10.1105/tpc.107.053371
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发表时间：
2007-11-01
期刊：
影响因子：
11.6
通讯作者：
Sweetlove, Lee J.
中科院分区：
文献类型：
--
作者：
Graham, James W. A.;Williams, Thomas C. R.;Sweetlove, Lee J.
在拟南芥中，糖酵解酶存在于线粒体表面，游离于胞浆中。这种双重定位的功能意义已经被证实，在拟南芥细胞和马铃薯(Solanum Tuberosum)块茎中，线粒体联合的程度取决于呼吸速率。因此，用KCN抑制呼吸导致结合程度成比例下降，而通过解偶联、组织老化或转化酶的过度表达刺激呼吸则导致线粒体结合增加。在所有处理中，细胞中糖酵解酶的总活性没有改变，表明每个酶的现有池在细胞质和线粒体之间重新分配。在分离的线粒体上进行的同位素稀释实验，使用C-13核磁共振波谱来监测未标记的糖酵解中间体对C-13标记的前体衍生的下游中间体产生的影响，为不同水平的底物通道的发生提供了直接证据。下拉实验表明，与线粒体膜外膜蛋白VDAC的相互作用，将糖酵解酶锚定在线粒体表面。糖酵解酶似乎与线粒体动态结合以支持呼吸作用，底物通道通过竞争代谢途径限制中间体的使用。
In Arabidopsis thaliana, enzymes of glycolysis are present on the surface of mitochondria and free in the cytosol. The functional significance of this dual localization has now been established by demonstrating that the extent of mitochondrial association is dependent on respiration rate in both Arabidopsis cells and potato (Solanum tuberosum) tubers. Thus, inhibition of respiration with KCN led to a proportional decrease in the degree of association, whereas stimulation of respiration by uncoupling, tissue ageing, or overexpression of invertase led to increased mitochondrial association. In all treatments, the total activity of the glycolytic enzymes in the cell was unaltered, indicating that the existing pools of each enzyme repartitioned between the cytosol and the mitochondria. Isotope dilution experiments on isolated mitochondria, using C-13 nuclear magnetic resonance spectroscopy to monitor the impact of unlabeled glycolytic intermediates on the production of downstream intermediates derived from C-13-labeled precursors, provided direct evidence for the occurrence of variable levels of substrate channeling. Pull-down experiments suggest that interaction with the outer mitochondrial membrane protein, VDAC, anchors glycolytic enzymes to the mitochondrial surface. It appears that glycolytic enzymes associate dynamically with mitochondria to support respiration and that substrate channeling restricts the use of intermediates by competing metabolic pathways.