Pelosin J M, Keramidas M, Souvignet C, Chambaz E M
INSERM U244, BRCE, LBIO, CEN.G, Grenoble, France.
Biochem Biophys Res Commun. 1990 Jun 29;169(3):1040-8. doi: 10.1016/0006-291x(90)91999-9.
Catalytic properties of protein kinase C isoforms purified from rat brain and bovine adrenocortical tissues were examined. The results showed that known inhibitors of PKC activity such as gossypol and H-7 were active on all the three isolated enzyme isoforms with similar IC50 values. However, whereas the type III brain isozyme activity was not affected by a preincubation with phosphatidylserine (PS), the same treatment resulted in a virtually complete loss of the type I and II isoform activities within 4 min at 30 degrees. This kinase inactivation caused by PS preincubation was prevented in the presence of ATP-Mg2+ or its competitive inhibitor H-7. These findings indicate that the type III isoform can clearly be distinguished from the other members of the PKC family by this specific property. This approach was used to confirm the characterization of the single form of PKC detected in bovine adrenocortical tissue as a type III isotype. This specific behavior toward phosphatidylserine suggests that the molecular organization of the phospholipid sensitive, regulatory domain of the PKC isoform III with regard to its catalytic site and thus its mechanism of activation may differ from that of other PKC isotypes.
对从大鼠脑和牛肾上腺皮质组织中纯化得到的蛋白激酶C同工型的催化特性进行了研究。结果表明，已知的蛋白激酶C活性抑制剂，如棉酚和H-7，对所有三种分离出的酶同工型均有活性，且IC50值相似。然而，虽然III型脑同工酶的活性不受与磷脂酰丝氨酸（PS）预孵育的影响，但相同处理在30℃下4分钟内导致I型和II型同工型的活性几乎完全丧失。PS预孵育引起的这种激酶失活在ATP-Mg2+或其竞争性抑制剂H-7存在时可被阻止。这些发现表明，III型同工型可通过这种特殊性质与蛋白激酶C家族的其他成员明显区分开来。该方法用于确认在牛肾上腺皮质组织中检测到的单一形式的蛋白激酶C为III型同工型。这种对磷脂酰丝氨酸的特殊行为表明，蛋白激酶C同工型III的磷脂敏感调节结构域相对于其催化位点的分子组织以及因此其激活机制可能与其他蛋白激酶C同工型不同。
