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首页> 外文期刊>Archives of Biochemistry and Biophysics >Incorporation of phosphate into glycogen by glycogen synthase
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Incorporation of phosphate into glycogen by glycogen synthase

机译：糖原合酶将磷酸盐掺入糖原中

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The storage polymer glycogen normally contains small amounts of covalently attached phosphate as phosphomonoesters at C2, C3 and C6 atoms of glucose residues. In the absence of the laforin phosphatase, as in the rare childhood epilepsy Lafora disease, the phosphorylation level is elevated and is associated with abnormal glycogen structure that contributes to the pathology. Laforin therefore likely functions in vivo as a glycogen phosphatase. The mechanism of glycogen phosphorylation is less well understood. We have reported that glycogen synthase incorporates phosphate into glycogen via a rare side reaction in which glucose-phosphate rather than glucose is transferred to a growing polyglucose chain (Tagliabracci et al. (2011) Cell Metab 13, 274-282). We proposed a mechanism to account for phosphorylation at C2 and possibly at C3. Our results have since been challenged (Nitschke et al. (2013) Cell Metab 17, 756-767). Here we extend the evidence supporting our conclusion, validating the assay used for the detection of glycogen phosphorylation, measurement of the transfer of P-32 from [beta-P-22]UDP-glucose to glycogen by glycogen synthase. The P-32 associated with the glycogen fraction was stable to ethanol precipitation, SOS-PAGE and gel filtration on Sephadex G50. The P-32-signal was not affected by inclusion of excess unlabeled UDP before analysis or by treatment with a UDPase, arguing against the signal being due to contaminating [beta-P-32]UDP generated in the reaction. Furthermore, [beta-P-32]UDP did not bind non-covalently to glycogen. The P-32 associated with glycogen was released by laforin treatment, suggesting that it was present as a phosphomonoester. The conclusion is that glycogen synthase can mediate the introduction of phosphate into glycogen, thereby providing a possible mechanism for C2, and perhaps C3, phosphorylation. (C) 2016 Elsevier Inc. All rights reserved.
机译：存储聚合物糖原通常在葡萄糖残基的C2，C3和C6原子处含有少量共价连接的磷酸酯作为磷酸单酯。如在少见的儿童癫痫性拉福拉氏病中缺乏拉福林磷酸酶，磷酸化水平升高，并与导致病理的糖原结构异常有关。因此，Laforin可能在体内起糖原磷酸酶的作用。糖原磷酸化的机制还不太清楚。我们已经报道了糖原合酶通过罕见的副反应将磷酸酯结合到糖原中，其中葡萄糖-磷酸而不是葡萄糖被转移到生长的聚葡萄糖链上（Tagliabracci et al。（2011）Cell Metab 13，274-282）。我们提出了一种机制来解释C2以及可能C3处的磷酸化。此后，我们的结果受到了挑战（Nitschke等人（2013）Cell Metab 17，756-767）。在这里，我们扩展了支持我们结论的证据，验证了用于检测糖原磷酸化，通过糖原合酶测量从β-P-22] UDP-葡萄糖到糖原的P-32转移的测定方法。与糖原部分相关的P-32对乙醇沉淀，SOS-PAGE和Sephadex G50上的凝胶过滤稳定。 P-32信号不受分析前加入过量的未标记UDP或UDPase处理的影响，该信号是由于污染反应中生成的[β-P-32] UDP而引起的。此外，β-P-32] UDP不与糖原非共价结合。通过糖精蛋白处理释放了与糖原相关的P-32，表明它以磷酸单酯形式存在。结论是糖原合酶可以介导将磷酸盐引入糖原中，从而为C2甚至C3磷酸化提供可能的机制。 （C）2016 Elsevier Inc.保留所有权利。

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