Niittylä Totte, Comparot-Moss Sylviane, Lue Wei-Ling, Messerli Gaëlle, Trevisan Martine, Seymour Michael D J, Gatehouse John A, Villadsen Dorthe, Smith Steven M, Chen Jychian, Zeeman Samuel C, Smith Alison M
Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom.
J Biol Chem. 2006 Apr 28;281(17):11815-8. doi: 10.1074/jbc.M600519200. Epub 2006 Mar 2.
We report that protein phosphorylation is involved in the control of starch metabolism in Arabidopsis leaves at night. sex4 (starch excess 4) mutants, which have strongly reduced rates of starch metabolism, lack a protein predicted to be a dual specificity protein phosphatase. We have shown that this protein is chloroplastic and can bind to glucans and have presented evidence that it acts to regulate the initial steps of starch degradation at the granule surface. Remarkably, the most closely related protein to SEX4 outside the plant kingdom is laforin, a glucan-binding protein phosphatase required for the metabolism of the mammalian storage carbohydrate glycogen and implicated in a severe form of epilepsy (Lafora disease) in humans.
我们报告称，蛋白质磷酸化参与了拟南芥叶片夜间淀粉代谢的调控。sex4（淀粉过量4）突变体的淀粉代谢速率大幅降低，该突变体缺乏一种预测为双特异性蛋白磷酸酶的蛋白质。我们已经证明这种蛋白质存在于叶绿体中，能够与葡聚糖结合，并且有证据表明它在淀粉颗粒表面调节淀粉降解的初始步骤。值得注意的是，植物界之外与SEX4关系最密切的蛋白质是拉福林，它是一种葡聚糖结合蛋白磷酸酶，是哺乳动物储存碳水化合物糖原代谢所必需的，并且与人类一种严重的癫痫形式（拉福拉病）有关。
