MECHANISM OF ACTION OF ACETOACETATE DECARBOXYLASE

膜糖蛋白和分泌糖蛋白的转运受 通过“质量控制”机制， 内质网中不正确折叠蛋白质的降解 （ER）。 涉及的分子是钙粘蛋白和钙连接蛋白， 特异性地结合到葡糖基化的 高甘露糖聚糖。 对于寡聚蛋白， (IgM五聚体和六聚体），一组额外的规则似乎 控制它们的运输，这样那些没有达到 保留了适当的四级结构。 内的序列 ~t的C-末端，蛋白质对照sIgM分选、保留和 当保守的Cys 575突变时， 单体被分泌。 该末端片段具有N-连接聚糖 在Gln 663，“这是保守的所有物种检查;当这 残基突变聚合再次被废除。 因此我们 对这种特定聚糖的详细结构感兴趣， CHO加工对聚合的一般影响。 初步工作 已着手建立分析限制， 灵敏度和分析N-连接聚糖的总体可行性 从免疫球蛋白（伊加，IgG，IgD）释放。 这些材料 已经有了更大的数量，预计聚糖 为随后的Igm分离组分研究提供了模型。 使用内切糖苷酶的释放效率（包括使用 几种洗涤剂），甲基化后的提取，以及整体 方法的重现性。 在这项初步研究中，我们应用 使用电喷雾分析完整聚糖分布的方法 离子化质谱（ESI MS），并进一步探测这些 碰撞诱导解离（Collision Induced Dissociation，CID） 没有 色谱分离和发散检测技术避免了 样品纯化。 所有样本均已分析，只有主要样本 离子已通过CID详细分析。

The transport of membrane and secreted glycoproteins is governed by "quality control" mechanisms that mediate the retention and degradation of improperly folded proteins in theendoplasmic reticulum (ER). The molecules involved are calretuculin and calnexin, which specifically bind to the non-reducing terminus of the glucosylated high mannose glycan previous to processing. For oligomeric proteins, (IgM pentamers and hexamers), an additional set of rules appears to govern their transport, such that proteins that have not achieved the proper quaternary structure are retained. Sequences within the C-terminus of the ~t, protein control sIgM sorting, retention, and degradation and when a conserved Cys575 is mutated large amounts of the monomer are secreted. This terminal piece has an N-linked glycan at Gln663,'which is conserved in all species examined; when this residue is mutated polymerization is again abrogated. Thus, we areinterested in the detailed structure of this specific glycan and the general effect of CHO processing on polymerization. Initial work has been undertaken to establish the analytical constraints, sensitivity, and overall feasibility of profiling N-linked glycans released from the immunoglobulins (IgA, IgG, IgD). These materials have been available in larger amounts and the glycans anticipated provide a model for subsequent studies with isolated fractions of Igm. Efficiency of release with endoglycosidases (including studies with several detergents), extraction after methylation, and the overall reproducibility of the method. In this preliminary study, we apply methodology to profile intact glycan distributions using electrospray ionization-mass spectrometry (ESI MS), and further probe these structures by collision-induced dissociation (CID). The absence of chromatographic separations and divergent detecting techniques avoids sample disproportionation. All samples have been profiled, only major ions have been analyzed in detail by CID.