Ueki H, Yamasaki Y, Higo K, Motoyashiki T, Kawabata H, Morita T
Department of Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Hiroshima, Japan.
Biol Pharm Bull. 1995 Feb;18(2):214-8. doi: 10.1248/bpb.18.214.
Sodium orthovanadate (vanadate) stimulated cAMP phosphodiesterase (PDE) and protein tyrosine kinase (PTK) activities and inhibited the phosphotyrosine phosphatase (PTPase) activity in the particulate of isolated rat fat pads. Okadaic acid never showed any increase in the PDE activity up to 1 microM. Amiloride inhibited in part both stimulations of PDE and PTK activities by vanadate. The particulate PTK activity had an optimal divalent ion requirement of 15 mM Mg+2+2 mM Mn+2 in the assay medium and was not inhibited by 1 mM N-ethylmaleimide, suggesting it to be a different type from the insulin receptor and cytosolic PTK activities. The PDE, PTK, and PTPase active fractions were separated from the solubilized particulate fraction on a DEAE-Sephacel column. PDE activity was increased by the addition of the PTK active fraction. A further increase was observed by using the PTK active fraction pretreated with 1 mM vanadate. In contrast, the addition of PTPase active fraction decreased the PDE activity. This decrease disappeared by using the PTPase active fraction pretreated with 1 mM vanadate. These results suggest that the PDE activity is in part regulated through a process involving the particulate PTK and PTPase activities sensitive to vanadate.
原钒酸钠（钒酸盐）刺激了环磷酸腺苷磷酸二酯酶（PDE）和蛋白酪氨酸激酶（PTK）的活性，并抑制了分离的大鼠脂肪垫微粒中的磷酸酪氨酸磷酸酶（PTPase）活性。冈田酸在浓度高达1 microM时从未显示出PDE活性的任何增加。氨氯地平部分抑制了钒酸盐对PDE和PTK活性的刺激。微粒PTK活性在测定介质中对二价离子的最佳需求为15 mM Mg²⁺ + 2 mM Mn²⁺，并且不受1 mM N-乙基马来酰亚胺的抑制，这表明它与胰岛素受体和胞质PTK活性属于不同类型。PDE、PTK和PTPase活性组分在DEAE-琼脂糖凝胶柱上从溶解的微粒组分中分离出来。加入PTK活性组分后PDE活性增加。用1 mM钒酸盐预处理PTK活性组分后观察到进一步增加。相反，加入PTPase活性组分降低了PDE活性。使用用1 mM钒酸盐预处理的PTPase活性组分后，这种降低消失了。这些结果表明，PDE活性部分是通过一个涉及对钒酸盐敏感的微粒PTK和PTPase活性的过程来调节的。
