Rousset M, Paris H, Chevalier G, Terrain B, Murat J C, Zweibaum A
Cancer Res. 1984 Jan;44(1):154-60.
The activities of glycogen synthase and phosphorylase were measured and compared to the growth-related variations of glycogen accumulation in three cultured human tumor cell lines: HT-29 (colon carcinoma); MeWo (malignant melanoma); and RT-4 (carcinoma of the urinary bladder). A similar pattern of variations in the enzyme activities was found in the three cell lines. The activities of the a + b forms of glycogen phosphorylase increased throughout the culture period. Maximal activity of phosphorylase a coincided with low intracellular concentrations of glycogen during the period of exponential growth. When the rate of cell division decreased, phosphorylase a activity also decreased while the glycogen levels increased. Glycogen synthase was almost entirely in b form during the entire culture period, i.e., in both the exponential and the stationary phases. In vitro incubation of the cellular extracts without NaF showed, however, that the enzyme could be partially converted to the a form by the endogenous phosphatases. The A0.5 values of the enzyme for glucose-6-phosphate (Glc-6-P) were of the same order of magnitude as the intracellular Glc-6-P concentrations which ranged from 2.2 to 5.4 mM (almost 10 times those reported in normal cells). Similar Glc-6-P values were obtained by two different extraction methods controlled by the intracellular ATP and ADP concentrations. The Km values for uridine-5'-diphosphoglucose were always 2 to 3 times lower than the intracellular uridine-5'-diphosphoglucose concentrations. These results suggest that: (a) in these tumor cells, glycogen is essentially synthesized by glycogen synthase b via an allosteric activation by intracellular Glc-6-P; (b) there is no obvious growth-related control of glycogen synthase activity; and (c) the activity of glycogen phosphorylase seems to be growth dependent with maximal phosphorylase a activities associated with the period of high division rate.
测定了糖原合酶和磷酸化酶的活性，并将其与三种培养的人肿瘤细胞系（HT - 29，结肠癌细胞；MeWo，恶性黑色素瘤细胞；RT - 4，膀胱癌细胞）中糖原积累的生长相关变化进行了比较。在这三种细胞系中发现了酶活性的相似变化模式。糖原磷酸化酶a + b形式的活性在整个培养期间都增加。在指数生长期，磷酸化酶a的最大活性与细胞内低糖原浓度同时出现。当细胞分裂速率下降时，磷酸化酶a的活性也下降，而糖原水平增加。在整个培养期间，糖原合酶几乎完全处于b形式，即在指数期和稳定期均如此。然而，在无NaF的情况下对细胞提取物进行体外孵育表明，该酶可被内源性磷酸酶部分转化为a形式。该酶对葡萄糖 - 6 - 磷酸（Glc - 6 - P）的A0.5值与细胞内Glc - 6 - P浓度处于相同数量级，细胞内Glc - 6 - P浓度范围为2.2至5.4 mM（几乎是正常细胞中报道值的10倍）。通过两种受细胞内ATP和ADP浓度控制的不同提取方法获得了相似的Glc - 6 - P值。尿苷 - 5'-二磷酸葡萄糖的Km值总是比细胞内尿苷 - 5'-二磷酸葡萄糖浓度低2至3倍。这些结果表明：（a）在这些肿瘤细胞中，糖原基本上是由糖原合酶b通过细胞内Glc - 6 - P的变构激活来合成的；（b）不存在明显的与生长相关的糖原合酶活性控制；（c）糖原磷酸化酶的活性似乎与生长相关，最大磷酸化酶a活性与高分裂率时期相关。
