Simultaneous and separable flux of pathways for glucose and glycogen utilization studied by 13C-NMR.
Simultaneous and separable flux of pathways for glucose and glycogen utilization studied by 13C-NMR.
复制标题
通过 13C-NMR 研究葡萄糖和糖原利用途径的同时和可分离通量。
DOI：
10.1006/jmcc.1994.1138
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发表时间：
1994
影响因子：
5
通讯作者：
Kushmerick,MJ
中科院分区：
文献类型：
--
作者：
Hardin,CD;Kushmerick,MJ
用~（13）C-NMR研究了猪颈动脉平滑肌对葡萄糖的利用和糖原的周转。在37°C下用C-1标记的葡萄糖对颈动脉段灌流8- 16小时后，13 C-NMR光谱显示大量掺入糖原、乳酸盐和在C-2和C-4位置暂时鉴定为谷氨酸盐的共振中。在未受刺激的肌肉中，净糖原掺入率在8h内近似线性。在洗去初始标记的葡萄糖后，在C-2标记的葡萄糖存在下，用80 mM KCl收缩颈动脉。在收缩过程中，观察到糖原分解和糖酵解的同时通量，产生标记在C-2位置的乳酸（从标记在第二个碳的葡萄糖），并与糖原共振的幅度降低。然而，在延长的收缩结束时，没有观察到在C-3位置标记的乳酸盐（来自C-3糖原）。如果两种途径的中间体完全混合，则会观察到来自葡萄糖和糖原的乳酸。当在5 mM NaCN存在下进行类似的实验以阻断氧化代谢时，则清楚地观察到源自葡萄糖和源自糖原的乳酸盐。因此，当氧化代谢是完整的，糖原分解和糖酵解的中间体通常不会出现完全混合，尽管在收缩过程中的两个途径的同时流量。这些可分离的胞质途径碳水化合物的利用提出了由反应扩散类的机制。胞质酶的这种组织可能代表细胞代谢的一般特征。
Glucose utilization and glycogen turnover was studied by13C-NMR in segments of hog carotid artery smooth muscle. After superfusion of carotid segments for 8-16h at 37°C with C-1 labeled glucose.13C-NMR spectra revealed substantial incorporation into glycogen, lactate and into resonances tentatively identified as glutamate at the C-2 and C-4 positions. The rate of net glycogen incorporation was approximately linear over 8h in unstimulated muscle. After washing out the initial labeled glucose, carotids were contracted by 80 mM KCl in the presence of C-2 labeled glucose. During the contraction simultaneous flux of glycogenolysis and glycolysis was observed with production of lactate labeled at the C-2 position (from glucose labeled at the second carbon) and with the magnitude of the glycogen resonance decreasing. However, no lactate labeled at the C-3 position (derived from C-3 glycogen) was observed at the end of a prolonged contraction. If complete mixing of the intermediates of the two pathways occurred, lactate derived from both glucose and glycogen would have been observed. When similar experiments are performed in the presence of 5 mM NaCN to block oxidative metabolism, then lactate derived from glucose and from glycogen was clearly observed. Therefore, when oxidative metabolism was intact, the intermediates of glycogenolysis and glycolysis did not normally appear to fully mix despite simultaneous flux of the two pathways during contraction. These separable cytosolic pathways for carbohydrate utilization are proposed to be governed by a reaction-diffusion class of mechanism. Such an organization of cytosolic enzymes may represent a general feature of cell metabolism.