Gilboe D P, Nuttall F Q
J Biol Chem. 1978 Jun 25;253(12):4078-81.
In normal fed rats, glycogen synthase D phosphatase activity in a glycogen pellet preparation was only partially inhibited (approximately 50%) by high concentrations of EDTA. However, the proportion of phosphatase activity inhibited by EDTA was markedly and rapidly (15 s) increased following glucagon or cAMP administration. Epinephrine administration did not alter the proportion of activity inhibited by EDTA. Glucose administration rapidly (2 min) reduced the proportion of synthase phosphatase activity inhibitable by EDTA. That is, the effect of glucose was just the opposite of that produced by glucagon or cAMP. Insulin administration had no effect on phosphatase activity. Synthase phosphatase activity assayed in the absence of EDTA was similar in all groups except for a moderate increase after glucose administration. Addition of Mg2+ completely reversed EDTA inhibition. Phosphorylase phosphatase activity in each group was not modified by addition of EDTA, although the percentage of phosphorylase in the alpha form was higher in glucagon-treated and lower in the glucose-treated animals as expected. These data suggest the presence of rapidly interconvertible forms of either synthase phosphatase or its substrate synthase D, detectable as a change in EDTA inhibitability and subject to glucose and glucagon control.
在正常喂食的大鼠中，糖原颗粒制剂中的糖原合酶D磷酸酶活性仅被高浓度的EDTA部分抑制（约50%）。然而，在给予胰高血糖素或cAMP后，EDTA抑制的磷酸酶活性比例显著且迅速（15秒）增加。给予肾上腺素并未改变EDTA抑制的活性比例。给予葡萄糖迅速（2分钟）降低了可被EDTA抑制的合酶磷酸酶活性比例。也就是说，葡萄糖的作用与胰高血糖素或cAMP产生的作用正好相反。给予胰岛素对磷酸酶活性无影响。除给予葡萄糖后有适度增加外，所有组在无EDTA情况下测定的合酶磷酸酶活性相似。添加Mg2+完全逆转了EDTA的抑制作用。尽管如预期的那样，在胰高血糖素处理的动物中α型磷酸化酶的百分比更高，而在葡萄糖处理的动物中更低，但每组中的磷酸化酶磷酸酶活性并未因添加EDTA而改变。这些数据表明存在合酶磷酸酶或其底物合酶D的快速相互转化形式，可检测为EDTA抑制性的变化，并受葡萄糖和胰高血糖素的控制。
