Tanaka T, Ito M, Ohmura T, Hidaka H
Biochemistry. 1985 Sep 10;24(19):5281-4. doi: 10.1021/bi00340a049.
Ca2+-dependent cyclic nucleotide phosphodiesterase (Ca2+-PDE) activity was stimulated by poly(L-aspartic acid) but not by poly(L-glutamic acid), poly(L-arginine), poly(L-lysine), and poly(L-proline). This activation was Ca2+ independent and did not further enhance the activation of Ca2+-PDE by Ca2+-calmodulin (CaM). Poly(L-aspartic acid) produced an increase in the Vmax of the phosphodiesterase, associated with a decrease in the apparent Km for the substrate, such being similar to results obtained with Ca2+-CaM. Poly(L-aspartic acid) did not significantly stimulate myosin light chain kinase and other types of cyclic nucleotide phosphodiesterase. CaM antagonists such as N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), trifluoperazine, and chlorpromazine selectively antagonized activation of the enzyme by poly(L-aspartic acid). Kinetic analysis of W-7-induced inhibition of activation of phosphodiesterase by poly(L-aspartic acid) was in a competitive fashion, and the Ki value was 0.19 mM. On the other hand, prenylamine, another type of calmodulin antagonist that binds to CaM at sites different from the W-7 binding sites, did not inhibit the poly(L-aspartic acid)-induced activation of Ca2+-dependent cyclic nucleotide phosphodiesterase. These results imply that poly(L-aspartic acid) is a calcium-independent activator of Ca2+-dependent phosphodiesterase and that aspartic acids in the CaM molecule may play an important role in the activation of Ca2+-PDE.
钙离子依赖的环核苷酸磷酸二酯酶（Ca2+-PDE）活性受到聚（L-天冬氨酸）的刺激，但不受聚（L-谷氨酸）、聚（L-精氨酸）、聚（L-赖氨酸）和聚（L-脯氨酸）的刺激。这种激活不依赖钙离子，并且不会进一步增强钙离子-钙调蛋白（CaM）对Ca2+-PDE的激活作用。聚（L-天冬氨酸）使磷酸二酯酶的Vmax增加，同时底物的表观Km降低，这与钙离子-CaM作用的结果相似。聚（L-天冬氨酸）不会显著刺激肌球蛋白轻链激酶和其他类型的环核苷酸磷酸二酯酶。CaM拮抗剂如N-（6-氨基己基）-5-氯-1-萘磺酰胺（W-7）、三氟拉嗪和氯丙嗪可选择性拮抗聚（L-天冬氨酸）对该酶的激活作用。对W-7诱导的聚（L-天冬氨酸）对磷酸二酯酶激活作用的抑制进行动力学分析，结果呈竞争性，Ki值为0.19 mM。另一方面，普尼拉明是另一种钙调蛋白拮抗剂，它与CaM的结合位点不同于W-7的结合位点，它不会抑制聚（L-天冬氨酸）诱导的钙离子依赖的环核苷酸磷酸二酯酶的激活。这些结果表明，聚（L-天冬氨酸）是钙离子依赖的磷酸二酯酶的非钙离子依赖性激活剂，并且CaM分子中的天冬氨酸可能在Ca2+-PDE的激活中起重要作用。
