Iwasa T, Fukunaga K, Yamamoto H, Tanaka E, Miyamoto E
Arch Biochem Biophys. 1984 Nov 15;235(1):212-7. doi: 10.1016/0003-9861(84)90270-4.
Glycogen synthase from skeletal muscle was phosphorylated by a Ca2+, calmodulin-dependent protein kinase from brain, with concomitant inactivation. About 0.7 mol phosphate/mol subunit was sufficient for a maximal inactivation of glycogen synthase. Further phosphorylation of the enzyme had no effect on the activity. The concentrations required to give half-maximal phosphorylation and inactivation of glycogen synthase were 1.1 and 0.5 microM for Ca2+, and 22 and 11 nM for calmodulin, respectively. The molar ratio of the subunit of the protein kinase to calmodulin was 2-3:1 for half-maximal phosphorylation and inactivation of glycogen synthase. The Km values for glycogen synthase and ATP were 3.6 and 114 microM, respectively, for phosphorylation. Phosphate was incorporated into sites Ia, Ib, and 2 on glycogen synthase, and site 2 was the most rapidly phosphorylated. These results indicate that the brain Ca2+, calmodulin-dependent protein kinase is probably involved in glycogen metabolism in the brain as a glycogen synthase kinase.
来自骨骼肌的糖原合酶被来自大脑的一种钙、钙调蛋白依赖性蛋白激酶磷酸化，并伴随失活。每摩尔亚基约0.7摩尔磷酸盐足以使糖原合酶最大程度失活。该酶的进一步磷酸化对活性没有影响。使糖原合酶达到最大磷酸化和失活一半所需的Ca²⁺浓度分别为1.1微摩尔和0.5微摩尔，钙调蛋白的浓度分别为22纳摩尔和11纳摩尔。对于糖原合酶达到最大磷酸化和失活一半，蛋白激酶亚基与钙调蛋白的摩尔比为2 - 3:1。磷酸化时，糖原合酶和ATP的Km值分别为3.6微摩尔和114微摩尔。磷酸盐被掺入糖原合酶的Ia、Ib和2位点，2位点是磷酸化最快的位点。这些结果表明，大脑的钙、钙调蛋白依赖性蛋白激酶可能作为糖原合酶激酶参与大脑中的糖原代谢。
