Oberdisse E, Lapetina E G
Biochem Biophys Res Commun. 1987 May 14;144(3):1188-96. doi: 10.1016/0006-291x(87)91437-9.
Guanosine 5'-O-thiotriphosphate (GTP gamma S) and thrombin stimulate the activity of phospholipase C in platelets that have been permeabilized with saponin and whose inositol phospholipids have been prelabeled with [3H]inositol. Ca2+ has opposite effects on the formation of [3H]inositol phosphates induced by thrombin or GTP gamma S. While the action of GTP gamma S on the formation of [3H]inositol phosphates is inhibited by Ca2+, action of thrombin is stimulated by Ca2+. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), which inhibits the function of GTP-binding proteins, also inhibits the effect of GTP gamma S on phospholipase C stimulation but, surprisingly, increases the effect of thrombin. Ca2+ increases the inhibitory effect of GDP beta S on GTP gamma S activation of phospholipase C, but Ca2+ further enhances the stimulatory effect of GDP beta S on the thrombin activation of phospholipase C. This indicates that two mechanisms are responsible for the activation of phospholipase C in platelets. A GTP-binding protein is responsible for regulation of phospholipase C induced by GTP gamma S, while the effect of thrombin on the stimulation of phospholipase C is independent of GTP-binding proteins. However, the effect of thrombin may be modulated by the action of an inhibitory GTP-binding protein.
5'-O-硫代三磷酸鸟苷（GTPγS）和凝血酶可刺激经皂角苷通透处理且肌醇磷脂已用[3H]肌醇预标记的血小板中磷脂酶C的活性。钙离子对凝血酶或GTPγS诱导的[3H]肌醇磷酸形成具有相反作用。虽然钙离子抑制GTPγS对[3H]肌醇磷酸形成的作用，但凝血酶的作用却受到钙离子的刺激。5'-O-（2-硫代二磷酸）鸟苷（GDPβS）抑制GTP结合蛋白的功能，它也抑制GTPγS对磷脂酶C刺激的作用，但令人惊讶的是，它会增强凝血酶的作用。钙离子增加GDPβS对GTPγS激活磷脂酶C的抑制作用，但钙离子进一步增强GDPβS对凝血酶激活磷脂酶C的刺激作用。这表明有两种机制负责血小板中磷脂酶C的激活。一种GTP结合蛋白负责调节由GTPγS诱导的磷脂酶C，而凝血酶对磷脂酶C刺激的作用独立于GTP结合蛋白。然而，凝血酶的作用可能受到抑制性GTP结合蛋白作用的调节。
