Newman J D, Armstrong J M
Biochim Biophys Acta. 1978 Dec 1;544(2):225-33. doi: 10.1016/0304-4165(78)90092-2.
A procedure was developed for determination of glycogen synthase and phosphorylase activities in liver after various in vivo physiological treatments. Liver samples were obtained from anaesthetised rats by freeze-clamping in situ. Other procedures were shown to stimulate the activity of phosphorylase and depress the activity of glycogen in the liver. The direction of glycogen metabolism appears to be regulated by the relative proportions of the two enzymes, as shown by a strong positive correlation between total activities and active forms of phosphorylase and synthase. The enzyme activities responded as expected to stimuli such as insulin and glucose, which depressed phosphorylase and increased synthase activity, and glucagon, which increased phosphorylase and decreased synthase activity. In fasted animals approximately 50% of each enzyme was in the active form, which suggests the existence of a potential futile cycle for glycogen metabolism. The role for such a cycle in the regulation of glycogen synthesis and degradation is discussed.
已开发出一种用于测定经各种体内生理处理后肝脏中糖原合酶和磷酸化酶活性的方法。通过原位冷冻钳夹从麻醉大鼠获取肝脏样本。其他程序显示可刺激磷酸化酶的活性并降低肝脏中糖原的活性。糖原代谢的方向似乎由这两种酶的相对比例调节，磷酸化酶和合成酶的总活性与活性形式之间的强正相关表明了这一点。酶活性对胰岛素和葡萄糖等刺激的反应符合预期，胰岛素会降低磷酸化酶活性并增加合成酶活性，而胰高血糖素会增加磷酸化酶活性并降低合成酶活性。在禁食动物中，每种酶约50%处于活性形式，这表明糖原代谢存在潜在的无效循环。讨论了这种循环在糖原合成和降解调节中的作用。
