Ashton A R, Burnell J N, Hatch M D
Arch Biochem Biophys. 1984 May 1;230(2):492-503. doi: 10.1016/0003-9861(84)90429-6.
These studies provide information about the mechanism of the light/dark-mediated regulation of pyruvate, Pi dikinase (EC 2.7.9.1) in leaves. It is shown that inactivation is due to a phosphorylation of the enzyme from the beta-phosphate of ADP, and that activation occurs by phosphorolysis to remove the enzyme phosphate group. During ADP plus ATP-dependent inactivation of pyruvate, Pi dikinase in chloroplast extracts, 32P was incorporated into the enzyme from [beta-32P]ADP. Approximately 1 mol of phosphate was incorporated per mol of monomeric enzyme subunit inactivated. There was very little incorporation of label from ADP or ATP labeled variously in other positions with 32P or from the nucleotides labeled with 3H in the purine ring. Purified pyruvate, Pi dikinase was also labeled from [beta-32P]ADP during inactivation. In this system, phosphorylation of the enzyme required the addition of the "regulatory protein" shown previously to be essential for catalyzing inactivation and activation. During orthophosphate-dependent reactivation of pyruvate, Pi dikinase, it was shown that the enzyme loses 32P label and that pyrophosphate is produced. The significance of these findings in relation to regulation of the enzyme in vivo is discussed.
这些研究提供了有关叶片中光/暗介导的丙酮酸、磷酸二激酶（EC 2.7.9.1）调控机制的信息。结果表明，失活是由于该酶从ADP的β-磷酸基团发生磷酸化作用，而激活则是通过磷酸解作用去除酶的磷酸基团来实现的。在叶绿体提取物中，丙酮酸、磷酸二激酶依赖ADP加ATP的失活过程中，32P从[β-32P]ADP掺入到该酶中。每摩尔失活的单体酶亚基大约掺入1摩尔磷酸。来自在其他位置用32P标记的ADP或ATP，或来自嘌呤环用3H标记的核苷酸的标记掺入量极少。纯化的丙酮酸、磷酸二激酶在失活过程中也从[β-32P]ADP获得标记。在这个系统中，酶的磷酸化需要添加先前已证明对催化失活和激活至关重要的“调节蛋白”。在丙酮酸、磷酸二激酶依赖正磷酸盐的再激活过程中，结果表明该酶失去32P标记并产生焦磷酸。讨论了这些发现与该酶在体内调控的相关性。
