Ramakrishna S, Pucci D L, Benjamin W B
J Biol Chem. 1981 Oct 25;256(20):10213-6.
ATP-citrate lyase was phosphorylated by highly purified cyclic AMP-independent protein kinase (ATP-citrate lyase kinase) or the catalytic subunit of cyclic AMP-dependent protein kinase. Each kinase phosphorylated ATP-citrate lyase equally but the combination of both kinases increased ATP-citrate lyase phosphorylation additively. When ATP-citrate lyase was phosphorylated with each kinase and partially digested with either L-1-tosylamido-2-phenylmethyl chloromethyl ketone-treated trypsin or Staphylococcus aureus protease followed by electrophoresis of the proteolytic products on sodium dodecyl sulfate-polyacrylamide gels or when the phosphorylated lyase was completely digested by these proteases followed by chromatography and electrophoresis, the results showed that the site phosphorylated by ATP-citrate lyase kinase was different from that phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase. Only phosphoserine was found in lyase phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase whereas phosphoserine and phosphothreonine were found in ATP-citrate lyase phosphorylated by lyase kinase.
ATP-柠檬酸裂解酶可被高度纯化的不依赖环磷酸腺苷的蛋白激酶（ATP-柠檬酸裂解酶激酶）或依赖环磷酸腺苷的蛋白激酶的催化亚基磷酸化。每种激酶对ATP-柠檬酸裂解酶的磷酸化程度相同，但两种激酶共同作用时，对ATP-柠檬酸裂解酶的磷酸化作用呈累加效应。当用每种激酶对ATP-柠檬酸裂解酶进行磷酸化，并用L-1-甲苯磺酰氨基-2-苯甲基氯甲基酮处理的胰蛋白酶或金黄色葡萄球菌蛋白酶进行部分消化，然后将蛋白水解产物在十二烷基硫酸钠-聚丙烯酰胺凝胶上进行电泳时，或者当磷酸化的裂解酶被这些蛋白酶完全消化，随后进行色谱分析和电泳时，结果表明，ATP-柠檬酸裂解酶激酶磷酸化的位点与依赖环磷酸腺苷的蛋白激酶的催化亚基磷酸化的位点不同。在依赖环磷酸腺苷的蛋白激酶的催化亚基磷酸化的裂解酶中仅发现磷酸丝氨酸，而在裂解酶激酶磷酸化的ATP-柠檬酸裂解酶中发现了磷酸丝氨酸和磷酸苏氨酸。
