Huang L C, Heimark D, Linko J, Nolan R, Larner J
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Biochem Biophys Res Commun. 1999 Feb 5;255(1):150-6. doi: 10.1006/bbrc.1999.0111.
Two inositol phosphoglycans (IPG) isolated from beef liver and designated as putative insulin mediators were demonstrated to reciprocally enhance the dephosphorylation of inhibitor-1 (INH-1) and DARPP-32, thus directly activating phosphatase 2C and disinhibiting phosphatase 1 in a potential protein phosphatase 2C --> phosphatase 1 cascade mechanism. One IPG termed pH 2.0, containing Dchiro-inositol and galactosamine, stimulated the dephosphorylation of INH-1 and DARPP-32 in a dose-dependent manner in the low micromolar range. A second, termed pH 1.3, containing myo-inositol glucosamine and mannose acted reciprocally to inhibit the cAMP-dependent protein kinase phosphorylation of INH-1 and DARPP-32 in a dose-dependent manner in the low micromolar range. These model experiments are discussed in terms of the observed dephosphorylation of INH-1 with insulin action documented in the literature and the activation of both phosphatase 1 and 2C described in intact cells and in vivo with insulin action.
从牛肝中分离出的两种肌醇磷酸聚糖（IPG）被指定为假定的胰岛素介质，它们被证明能相互增强抑制剂-1（INH-1）和DARPP-32的去磷酸化，从而在潜在的蛋白磷酸酶2C→蛋白磷酸酶1级联机制中直接激活蛋白磷酸酶2C并解除对蛋白磷酸酶1的抑制。一种名为pH 2.0的IPG含有D-手性肌醇和半乳糖胺，在低微摩尔范围内以剂量依赖的方式刺激INH-1和DARPP-32的去磷酸化。另一种名为pH 1.3的IPG含有肌醇葡糖胺和甘露糖，在低微摩尔范围内以剂量依赖的方式相互作用，抑制INH-1和DARPP-32的cAMP依赖性蛋白激酶磷酸化。这些模型实验是根据文献中记载的胰岛素作用下INH-1的去磷酸化以及完整细胞和体内胰岛素作用下蛋白磷酸酶1和2C的激活来讨论的。
