Gilboe D P, Nuttall F Q
FEBS Lett. 1984 May 21;170(2):365-9. doi: 10.1016/0014-5793(84)81345-9.
Recent studies indicate that glucose directly stimulates synthase phosphatase activity in vitro but only at high, non-physiological concentrations. Present results demonstrate that at a physiological concentration glucose can be stimulatory, provided that an appropriate second effector is present. Caffeine and adenosine are examples of such effectors which act synergistically with glucose to enhance synthase phosphatase activity. Caffeine but not adenosine enhances glucose stimulation of phosphorylase phosphatase activity. In the absence of glucose, caffeine but not adenosine stimulates both synthase and phosphorylase phosphatase reactions. Thus, glucose regulation of glycogen synthase activation in vivo could require a second effector. Neither the identity nor source of such an effector is known. The putative regulator could be a mediator for a hormone such as insulin. The present work suggests that the chemical nature of the effector might be that of a derivatized purine of which nucleosides are an example.
最近的研究表明，葡萄糖在体外直接刺激合酶磷酸酶活性，但仅在高的、非生理浓度下。目前的结果表明，在生理浓度下，只要存在适当的第二效应物，葡萄糖就可以起到刺激作用。咖啡因和腺苷就是这样的效应物的例子，它们与葡萄糖协同作用以增强合酶磷酸酶活性。咖啡因而非腺苷增强葡萄糖对磷酸化酶磷酸酶活性的刺激。在没有葡萄糖的情况下，咖啡因而非腺苷刺激合酶和磷酸化酶磷酸酶反应。因此，体内糖原合酶激活的葡萄糖调节可能需要第二效应物。这种效应物的身份和来源均未知。假定的调节因子可能是胰岛素等激素的介质。目前的工作表明，效应物的化学性质可能是一种衍生嘌呤，核苷就是其中的一个例子。
