Andersen B, Rassov A, Westergaard N, Lundgren K
Department of Diabetes Biochemistry and Metabolism, Novo Nordisk A/S, Building C9.S19, Novo Nordisk Park, DK-2760 Mâlov, Denmark.
Biochem J. 1999 Sep 15;342 Pt 3(Pt 3):545-50.
1,4-Dideoxy-1,4-imino-d-arabinitol (DAB) was identified previously as a potent inhibitor of both the phosphorylated and non-phosphorylated forms of glycogen phosphorylase (EC 2.4.1.1). In the present study, the effects of DAB were investigated in primary cultured rat hepatocytes. The transport of DAB into hepatocytes was dependent on time and DAB concentration. The rate of DAB transport was 192 pmol/min per mg of protein per mM DAB(medium-concentration). In hepatocytes, DAB inhibited basal and glucagon-stimulated glycogenolysis with IC(50) values of 1.0+/-0.3 and 1.1+/-0.2 microM, respectively. The primary inhibitory effect of DAB on glycogenolysis was shown to be due to inhibition of glycogen phosphorylase but, at higher concentrations of DAB, inhibition of the debranching enzyme (4-alpha-glucanotransferase, EC 2.4.1.25) may have an effect. No effects on glycogen synthesis were observed, demonstrating that glycogen recycling does not occur in cultured hepatocytes under the conditions tested. Furthermore, DAB had no effects on phosphorylase kinase, the enzyme responsible for phosphorylation and thereby activation of glycogen phosphorylase, or on protein phosphatase 1, the enzyme responsible for inactivation of glycogen phosphorylase through dephosphorylation.
1,4-二脱氧-1,4-亚氨基-D-阿拉伯糖醇（DAB）先前被鉴定为糖原磷酸化酶（EC 2.4.1.1）的磷酸化和非磷酸化形式的有效抑制剂。在本研究中，研究了DAB对原代培养大鼠肝细胞的影响。DAB进入肝细胞的转运取决于时间和DAB浓度。DAB的转运速率为每毫克蛋白质每分钟192皮摩尔每毫摩尔DAB（培养基浓度）。在肝细胞中，DAB抑制基础和胰高血糖素刺激的糖原分解，IC（50）值分别为1.0±0.3和1.1±0.2微摩尔。DAB对糖原分解的主要抑制作用表明是由于抑制糖原磷酸化酶，但在较高浓度的DAB下，脱支酶（4-α-葡聚糖转移酶，EC 2.4.1.25）的抑制可能会产生影响。未观察到对糖原合成的影响，表明在所测试的条件下培养的肝细胞中不发生糖原循环。此外，DAB对磷酸化酶激酶（负责磷酸化并由此激活糖原磷酸化酶的酶）或对蛋白磷酸酶1（负责通过去磷酸化使糖原磷酸化酶失活的酶）没有影响。
