Rigoulet M, Leverve X M, Plomp P J, Meijer A J
Laboratory of Biochemistry, University of Amsterdam, The Netherlands.
Biochem J. 1987 Aug 1;245(3):661-8. doi: 10.1042/bj2450661.
Control properties of the gluconeogenic pathway in hepatocytes isolated from starved rats were studied in the presence of glucose. The following observations were made. (1) Glucose stimulated the rate of glucose production from 20 mM-glycerol, from a mixture of 20 mM-lactate and 2 mM-pyruvate, or from pyruvate alone; no stimulation was observed with 20 mM-alanine or 20 mM-dihydroxyacetone. Maximal stimulation was obtained between 2 and 5 mM-glucose, depending on the conditions. At concentrations above 6 mM, gluconeogenesis declined again, so that at 10 mM-glucose the glucose production rate became equal to that in its absence. (2) With glycerol, stimulation of gluconeogenesis by glucose was accompanied by oxidation of cytosolic NADH and reduction of mitochondrial NAD+ and was insensitive to the transaminase inhibitor amino-oxyacetate; this indicated that glucose accelerated the rate of transport of cytosolic reducing equivalents to the mitochondria via the glycerol 1-phosphate shuttle. (3) With lactate plus pyruvate (10:1) as substrates, stimulation of gluconeogenesis by glucose was almost additive to that obtained with glucagon. From an analysis of the effect of glucose on the curves relating gluconeogenic flux and the steady-state intracellular concentrations of gluconeogenic intermediates under various conditions, in the absence and presence of glucagon, it was concluded that addition of glucose stimulated both phosphoenolpyruvate carboxykinase and pyruvate carboxylase activity.
在有葡萄糖存在的情况下，研究了从饥饿大鼠分离的肝细胞中糖异生途径的调控特性。得到了以下观察结果。（1）葡萄糖刺激了从20 mM甘油、20 mM乳酸和2 mM丙酮酸的混合物或仅从丙酮酸生成葡萄糖的速率；而20 mM丙氨酸或20 mM二羟基丙酮则未观察到刺激作用。根据条件不同，在2至5 mM葡萄糖之间可获得最大刺激。在浓度高于6 mM时，糖异生作用再次下降，因此在10 mM葡萄糖时，葡萄糖生成速率变得与无葡萄糖时相等。（2）对于甘油，葡萄糖对糖异生的刺激伴随着胞质NADH的氧化和线粒体NAD⁺的还原，并且对转氨酶抑制剂氨基氧乙酸不敏感；这表明葡萄糖通过磷酸甘油穿梭加速了胞质还原当量向线粒体的转运速率。（3）以乳酸加丙酮酸（10:1）作为底物时，葡萄糖对糖异生的刺激与胰高血糖素所产生的刺激几乎具有加和性。通过分析在有无胰高血糖素的各种条件下，葡萄糖对糖异生通量与糖异生中间产物稳态细胞内浓度之间关系曲线的影响，得出添加葡萄糖刺激了磷酸烯醇式丙酮酸羧激酶和丙酮酸羧化酶的活性。
