LIPID-LINKED SACCHARIDES IN GLYCOPROTEIN SYNTHESIS

N-连接糖蛋白是许多真核细胞中的重要受体， 而这些类型的分子与各种识别有关 细胞-细胞相互作用、寄主-寄生虫和寄主-共生体等现象 相互作用，以及许多具有生物重要性的模型分子的结合。 因此，这些类型的糖蛋白在这种情况下可能具有特殊的意义 癌症、动脉粥样硬化和糖尿病等疾病。少校 这项建议的目的是了解生物合成的机制。 以及这些N-连接的寡糖部分的加工 糖蛋白。在这些研究中将采取两种方法。在……里面 第一种情况下，我们会溶解大量的糖基转移酶和 尽可能处理糖苷酶，对其进行一定程度的纯化，并进行研究 他们的财产。我们将特别关注其特殊性 关于所使用的底物和形成的产品的性质 在每个反应中。在初步研究中，我们已经发现一些 合成脂联低聚糖的活性可以是 通过用NP-40处理大豆细胞膜来增溶。我们还有 脂连接低聚糖用作这些酶的受体 我们可以用可溶的形式对它们进行检测。因此，我们已经准备好继续 一些提纯研究。我们还检测到葡萄糖苷酶和 溶解部分中甘露糖苷酶活性的测定 酶与低聚糖底物，我们有可用的。所以我们 应该也可以在这里进行提纯。这些酶将 与底物特异性有关的特别感兴趣的 利用低聚糖。在第二种方法中，我们将提取 生长在德克萨斯州的各种野生植物，已知对 家畜，寻找糖蛋白加工的抑制剂。这个想法是 基于溶酶体抑制剂苦马豆素的发现 α-甘露糖苷酶和糖蛋白加工，在几种有毒物质中发现 植物，即澳大利亚植物Swainsona canescens和美国 疯草。由于苦马豆素有3个不对称羟基，似乎 其他种类的疯草或其他植物很可能会有 苦马豆素的立体异构体，可能抑制其他糖苷酶。

N-linked glycoproteins are important receptors in many eucaryotic cells, and these types of molecules have been implicated in various recognition phenomena including cell-cell interactions, host-parasite and host-symbiote interactions, and the binding of many biologically-important modlecules. Thus, these types of glycoproteins may be of especial significance in such disease conditions as cancer, atherosclerosis and diabetis. The major objective of this proposal is to understand the mechanism of biosynthesis and processing of the oligosaccharide portion of these N-linked glycoproteins. The approach to be taken in these studies is twofold. In the first case, we will solubilize as many of the glycosyl transferases and processing glycosidases as possible, purify them to some extent, and study their properties. We will be particularly concerned with the specificity with regard to substrate utilized and to the nature of the product formed in each reaction. In preliminary studies, we have already found that some of the activity for synthesizing the lipid-linked oligosaccharides can be solubilized by treating soybean cell membranes with NP-40. We also have lipid-linked oligosaccharides to use as acceptors with these enzymes so that we can assay them in soluble form. Thus we are ready to proceed with some purification studies. We have also detected glucosidase and mannosidase activities in the solubilized fraction and can assay these enzymes with oligosaccharide substrates that we have available. So we should also be able to proceed with purification here. These enzymes will be of special interest with regard to substrate specificity of the oligosaccharides utilized. In the second type of approach, we will extract various wild plants that grow in Texas, and are known to be toxic for livestock, to look for inhibitors of glycoprotein processing. This idea is based on the finding that swainsonine, an inhibitor of lysosomal Alpha-mannosidase and glycoprotein processing, is found in several toxic plants, i.e., the australian plant Swainsona canescens and american locoweed. Since swainsonine has 3 assymetric hydroxyl groups, it seems likely that other species of locoweed, or other plants, will have stereoisomers of swainsonine which may inhibit other glycosidases.