Sharma R K, Wirch E, Wang J H
J Biol Chem. 1978 May 25;253(10):3575-80.
An inhibitor protein of cyclic nucleotide phosphodiesterase is demonstrated in bovine brain extract and separated from modulator binding protein, a recently discovered inhibitory factor of phosphodiesterase. The new inhibitor protein is similar to the cyclic AMP phosphodiesterase inhibitor from bovine retina (Dumler, I. L., and Etingof, F. N. 1976) Biochim. Biophys, Acta 429, 474-484) in its heat stability: it retains full activity upon heating in a boiling water bath for 2 min. The new inhibitor protein counteracts the activation of the Ca2+-activatable cyclic nucleotide phosphodiesterase by the Ca2+-dependent modulator protein without affecting the basal activity of the enzyme. The inhibition of phosphodiesterase by the inhibitor can be reversed by high concentrations of modulator protein but is not influenced by a 20-fold increase in Ca2+ concentration. In contrast, a Ca2+-independent form of cyclic nucleotide phosphodiesterase is not inhibited by the inhibitor protein. These results suggest that the heat-stable inhibitor protein is specific against the action of the Ca2+-dependent modulator protein. Gel filtration analyses on Sephadex G-75 and G-100 columns have shown that the inhibitor protein and the modulator protein may associate in the presence of Ca2+. The molecular weights determined by the gel filtration for the free inhibitor protein and the complex of the inhibitor and modulator protein are about 70,000 and 85,000, respectively.
在牛脑提取物中发现了一种环核苷酸磷酸二酯酶抑制蛋白，并将其与调节子结合蛋白分离开来，调节子结合蛋白是最近发现的一种磷酸二酯酶抑制因子。这种新的抑制蛋白在热稳定性方面与来自牛视网膜的环磷酸腺苷磷酸二酯酶抑制剂相似（杜姆勒，I. L.，和埃廷诺夫，F. N. 1976）《生物化学与生物物理学报》429，474 - 484）：在沸水浴中加热2分钟后仍保留全部活性。这种新的抑制蛋白可抵消钙离子依赖性调节蛋白对钙离子激活的环核苷酸磷酸二酯酶的激活作用，而不影响该酶的基础活性。该抑制剂对磷酸二酯酶的抑制作用可被高浓度的调节蛋白逆转，但不受钙离子浓度增加20倍的影响。相比之下，一种不依赖钙离子的环核苷酸磷酸二酯酶形式不受该抑制蛋白的抑制。这些结果表明，这种热稳定的抑制蛋白对钙离子依赖性调节蛋白的作用具有特异性。在Sephadex G - 75和G - 100柱上进行的凝胶过滤分析表明，在钙离子存在的情况下，抑制蛋白和调节蛋白可能会结合。通过凝胶过滤测定的游离抑制蛋白以及抑制蛋白与调节蛋白复合物的分子量分别约为70,000和85,000。
