Makeeva V F, Lianova N B, Poglazov B F, Risnik V V, Gusev N B
Biokhimiia. 1989 Sep;54(9):1434-9.
Pigeon and chicken skeletal muscle phosphorylase kinase purified to a nearly homogeneous state is able to phosphorylate both cardiac and skeletal troponin I and T. After 1-hr incubation, the enzyme transfers up to 0.35 mole of phosphorus per mole of skeletal troponin I, up to 0.5 mole of cardiac troponin I and up to 0.1 mole of cardiac and skeletal troponin T. Avian muscle phosphorylase kinase does not phosphorylate the first serine residue of cardiac and skeletal troponin T, but catalyzes the phosphate incorporation into the site(s) of troponin T located in the central or C-terminal parts of the protein molecule. The rate of troponin phosphorylation by pigeon muscle phosphorylase kinase is pH-dependent: the 6.8/8.2 ratio for troponin I is close to 0,2, whereas that with troponin T varies in the range of 0.5-0.7. Troponin phosphorylation by avian phosphorylase kinase depends on the presence of Ca2+ in the incubation mixture. In the presence of 3 mM EGTA troponin I phosphorylation is inhibited by 70-90%, whereas that of troponin T--by 50%. The experimental results indicate that the phosphorylation of troponin I and T is catalyzed either by two different active centers or by different conformations of the single center of avian phosphorylase kinase.
纯化至近乎均一状态的鸽和鸡骨骼肌磷酸化酶激酶能够磷酸化心肌和骨骼肌肌钙蛋白I及T。孵育1小时后，该酶每摩尔骨骼肌肌钙蛋白I转移多达0.35摩尔磷，每摩尔心肌肌钙蛋白I转移多达0.5摩尔磷，每摩尔心肌和骨骼肌肌钙蛋白T转移多达0.1摩尔磷。禽肌肉磷酸化酶激酶不磷酸化心肌和骨骼肌肌钙蛋白T的第一个丝氨酸残基，但催化磷掺入位于蛋白质分子中央或C末端部分的肌钙蛋白T位点。鸽肌肉磷酸化酶激酶对肌钙蛋白的磷酸化速率取决于pH值：肌钙蛋白I的6.8/8.2比率接近0.2，而肌钙蛋白T的该比率在0.5 - 0.7范围内变化。禽磷酸化酶激酶对肌钙蛋白的磷酸化取决于孵育混合物中Ca2+的存在。在存在3 mM乙二醇双四乙酸（EGTA）的情况下，肌钙蛋白I的磷酸化被抑制70 - 90%，而肌钙蛋白T的磷酸化被抑制50%。实验结果表明，肌钙蛋白I和T的磷酸化要么由两个不同的活性中心催化，要么由禽磷酸化酶激酶单一中心的不同构象催化。
