Des Rosiers C, Fernandez C A, David F, Brunengraber H
Department of Nutrition, University of Montreal, Quebec, Canada.
J Biol Chem. 1994 Nov 4;269(44):27179-82.
The reversal of the mitochondrial isocitrate dehydrogenase reaction was investigated in rat livers perfused with [U-13C5]glutamate or [U-13C5]glutamine. The mass isotopomer distribution of citric acid cycle intermediates extracted from the livers was determined by gas chromatography-mass spectrometry. Citrate was enriched in an isotopomer containing five 13C. The formation of this isotopomer can only be explained by the reversal of the isocitrate dehydrogenase reaction. Calculation of kinetic parameters from the mass isotopomer data reveals a rapid interconversion of isocitrate and alpha-ketoglutarate. This interconversion results in an isotopic exchange between carbon 6 of citrate and mitochondrial CO2 that can affect the calculation of citric acid cycle kinetic parameters. Thus, the reversal of the isocitrate dehydrogenase reaction should be included in isotope labeling models of the citric acid cycle.
在灌注了[U-13C5]谷氨酸或[U-13C5]谷氨酰胺的大鼠肝脏中，研究了线粒体异柠檬酸脱氢酶反应的逆向过程。通过气相色谱-质谱法测定从肝脏中提取的柠檬酸循环中间产物的质量同位素异构体分布。柠檬酸在含有五个13C的同位素异构体中富集。这种同位素异构体的形成只能通过异柠檬酸脱氢酶反应的逆向过程来解释。从质量同位素异构体数据计算动力学参数表明，异柠檬酸和α-酮戊二酸之间存在快速相互转化。这种相互转化导致柠檬酸的C6与线粒体CO2之间发生同位素交换，这可能会影响柠檬酸循环动力学参数的计算。因此，异柠檬酸脱氢酶反应的逆向过程应纳入柠檬酸循环的同位素标记模型中。
