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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Differential regulation of bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase isoenzymes by cyclic AMP-dependent protein kinase and calmodulin-dependent phosphatase.
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Differential regulation of bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase isoenzymes by cyclic AMP-dependent protein kinase and calmodulin-dependent phosphatase.

机译：牛脑钙调蛋白依赖性环核苷酸磷酸二酯酶同工酶的差异调节取决于环AMP依赖性蛋白激酶和钙调蛋白依赖性磷酸酶。

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摘要

Purified bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase (3',5'-cyclic-nucleotide 5'-nucleotidohydrolase, EC 3.1.4.17) contains isozymes that are composed of two distinct subunits with molecular masses of 60,000 and 63,000 daltons. Analysis by NaDodSO4 gel electrophoresis and autoradiography of a phosphodiesterase sample phosphorylated in the presence of [32P]ATP and bovine heart cAMP-dependent protein kinase catalytic subunit revealed that only the 60-kDa subunit was phosphorylated. By using an isozyme preparation greatly enriched with the 60-kDa subunit, the following observations regarding the subunit phosphorylation were made. First, the phosphorylation resulted in the maximal incorporation of about 2 mol of phosphate per mol of subunit. Second, complete inhibition of 60-kDa subunit phosphorylation was approached at a saturating concentration of Ca2+ when a molar ratio of calmodulin to phosphodiesterase of 2:1 was used. No inhibition was observed in the presence of either Ca2+ or calmodulin alone. Third, the phosphorylation was accompanied by a decrease in the enzyme affinity for calmodulin; calmodulin concentrations required for 50% activation of nonphosphorylated and maximally phosphorylated phosphodiesterase isozyme samples were 0.51 and 9.3 nM, respectively. Fourth, the phosphodiesterase isozyme could be dephosphorylated by the calmodulin-dependent phosphatase (calcineurin) in the presence of Ni2+ or Mn2+, the dephosphorylation being associated with an increase in the enzyme affinity for calmodulin. Fifth, peak II rabbit liver phosphoprotein phosphatase catalytic unit did not catalyze the dephosphorylation of the phosphodiesterase isozyme.
机译：纯化的牛脑钙调蛋白依赖性环状核苷酸磷酸二酯酶（3'，5'-环状核苷酸5'-核苷酸水解酶，EC 3.1.4.17）含有同工酶，该同工酶由两个截然不同的亚基组成，分子量分别为60,000和63,000道尔顿。通过NaDodSO4凝胶电泳和放射自显影分析在[32P] ATP和牛心脏cAMP依赖性蛋白激酶催化亚基存在下被磷酸化的磷酸二酯酶样品，发现只有60-kDa亚基被磷酸化。通过使用富含60kDa亚基的同工酶制剂，对亚基的磷酸化进行了以下观察。首先，磷酸化导致每摩尔亚基最大掺入约2摩尔磷酸盐。其次，当钙调蛋白与磷酸二酯酶的摩尔比为2：1时，在饱和的Ca2 +浓度下，完全抑制60-kDa亚基的磷酸化。单独存在Ca2 +或钙调蛋白时未观察到抑制作用。第三，磷酸化伴随着对钙调蛋白的酶亲和力的降低。未磷酸化和最大磷酸化的磷酸二酯酶同工酶50％激活所需的钙调蛋白浓度分别为0.51和9.3 nM。第四，在Ni 2+或Mn 2+的存在下，磷酸二酯酶同工酶可以被钙调蛋白依赖性磷酸酶（钙调神经磷酸酶）去磷酸化，该去磷酸化与酶对钙调蛋白的亲和力的增加有关。第五，峰值II的兔肝磷酸化蛋白磷酸酶催化单元不能催化磷酸二酯酶同工酶的去磷酸化。

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