Ramakrishna S, Pucci D L, Benjamin W B
Biochem Biophys Res Commun. 1984 Aug 16;122(3):1047-56. doi: 10.1016/0006-291x(84)91197-5.
ATP-citrate lyase is phosphorylated in vivo at three amino acid residues on two peptide sequences (peptides a and b). Insulin action is known to increase the phosphorylation of peptide a. To study the effect of insulin on peptide b phosphorylation ATP-citrate lyase was radiolabeled in vivo by incubating fat pads with 32Pi. Following "cold chase", insulin action decreased the calculated specific radioactivity of peptide b to less than 30% of control whereas the specific radioactivity of peptide a increased 5-6 fold. The insulin induced decrease in peptide b phosphorylation was mainly due to a decrease in phosphothreonine phosphorylation. Isoproterenol treatment increased peptide a phosphorylation 4-6 fold but did not decrease peptide b phosphorylation. Specific radioactivity of ATP did not change significantly with hormone treatment. These results suggest that insulin action increases the dephosphorylation of peptide b by increasing the activity of a putative phosphothreonine phosphatase.
ATP-柠檬酸裂解酶在体内两个肽序列（肽a和肽b）的三个氨基酸残基处发生磷酸化。已知胰岛素作用可增加肽a的磷酸化。为研究胰岛素对肽b磷酸化的影响，通过用32Pi孵育脂肪垫在体内对ATP-柠檬酸裂解酶进行放射性标记。“冷追踪”后，胰岛素作用使肽b的计算比放射性降低至对照的30%以下，而肽a的比放射性增加了5至6倍。胰岛素诱导的肽b磷酸化减少主要是由于磷酸苏氨酸磷酸化的减少。异丙肾上腺素处理使肽a磷酸化增加4至6倍，但未降低肽b磷酸化。激素处理后ATP的比放射性没有显著变化。这些结果表明，胰岛素作用通过增加一种假定的磷酸苏氨酸磷酸酶的活性来增加肽b的去磷酸化。
