TWO REGULATORY ENZYMES OF DOLICHOL-LINKED GLYCOSYLATION

描述(研究人员摘要)：寡糖附着在 天冬酰胺在多种真核细胞中的残留 膜相关蛋白，如酶、激素、受体、 细胞外基质蛋白，以及质膜蛋白和 亚细胞器。N-连接糖蛋白的生物学特性各不相同 糖链的功能和作用不同于蛋白质 为了蛋白质。在某些情况下，多聚糖直接作用于 糖蛋白的生物活性，在其他情况下，糖蛋白影响 蛋白质的物理化学性质。中的许多初始步骤 糖链部分的复杂生物合成途径是常见的，无论是 最终加工的结构。最近的工作集中在理解 对这一途径的调节。要使用的方法是生化 第一：纯化的酶的活性的鉴定和重建 并确定单个酶水平的变化是如何在 活体影响整个糖基化途径的活性。克莱格医生是 专注于两种酶，UDP-N-乙酰氨基葡萄糖：多氯乙酸磷酸酯 N-乙酰氨基葡萄糖-1-磷酸转移酶和甘露硫磷二醇 合成酶。转移酶是反应途径的早期酶， 该合酶位于该途径的分支点。这个 假设这两种酶都是体内重要的调节酶 N-连接糖蛋白葡萄糖部分的生物合成途径。 这项提案中概述的研究将直接检验这一假设。

DESCRIPTION (Investigator's Abstract): Oligosaccharides are attached to asparagine residues in a wide variety of eukaryotic soluble and membrane-associated proteins such as enzymes, hormones, receptors, extracellular matrix proteins, and the proteins of the plasma membrane and subcellular organelles. N-linked glycoproteins vary as to their biological function and the role of the glycan in that function differs from protein to protein. In some cases, the glycan plays a direct role in the glycoprotein's biological activity and in other cases the glycan affects the protein's physicochemical properties. Many of the initial steps in the complex biosynthetic pathway of the glycan moiety are common regardless of the final processed structure. Recent work has focused on understanding the regulation of this pathway. The approach to be used is a biochemical one: to characterize and reconstitute the activity of purified enzymes in vitro and to determine how alterations in an individual enzyme level in vivo effects the activity of the entire glycosylation pathway. Dr. Krag is concentrating on two enzymes, UDP-N-acetylglucosamine:dolichyl phosphate N-acetylglucosamine-1-phosphate transferase and mannosylphosphoryldolichol synthase. The transferase is an enzyme early in the reaction pathway and the synthase is positioned at a branch point in the pathway. The hypothesis is that both these enzymes are important regulatory enzymes in the biosynthetic pathway of the glucose moiety of N-linked glycoproteins. The studies outlined in this proposal will directly test this hypothesis.