GLYCOLIPID AND GLYCOPROTEIN METABOLISM IN EYE TISSUE

视紫红质的碳水化合物链与 其他天冬酰胺连接的糖蛋白，表明存在 控制其生物合成的特殊机制。我们希望 调查这一监管过程。(1)我们将研究 其低聚糖的组装受到影响的可能性 通过在视蛋白的多肽骨架中编码的信号。一把钥匙 形成复合型低聚糖的步骤 链将是将GlcNAc残基添加到α(1- 6)-视紫红质的主要低聚糖的甘露糖臂。什么 指示视网膜在视紫红质上没有这种结构？(A)在 为了探索多肽对这一反应的影响， 我们将检测纯化的GlcNAc-转移酶II的活性 从大鼠肝脏中提取，以及从 以纯化的视紫红质低聚糖为受体的视网膜 与使用视蛋白、视紫红质或 含有这种低聚糖的糖肽。(二)我们 还应检查同一材料中视紫红质的半乳糖化 举止。(C)我们会改变视黄素的一级结构 将氨基酸类似物加入到多肽中，并 检测这种改变对糖基化的影响。 牛视紫质。(2)我们将探索视网膜的高尔基体 β-半乳糖苷酶和外己糖胺酶的存在 使用视蛋白的相关类似物作为底物的活动。(3)我们 应对加工过程中的寡糖进行表征 参与视紫红质糖基化的中间体。Pre- 在杆状细胞的内节段区域合成的视蛋白将 通过免疫学技术被分离出来。低聚糖 将被酶解出，并对其结构进行研究。 还将检查加工抑制剂的效果。这个 高效液相分析技术，加酶和化学分析技术 还将审查处理过程。通过分析的技术 高效液相色谱法，加上酶和化学降解，将用于 所有这些研究。 我们将继续我们的研究，涉及新陈代谢调节 二羟甲基苯酚的途径。在此之前，我们已经证明了多效酚-P- 甘露糖作为酶的变构激活剂 催化该途径的第一个反应。我们将研究一下 Dolicol途径的其他中间体对 激活现象。这些调查可能会揭示 控制糖蛋白这一关键方面的其他方面 生物合成。视网膜葡萄糖苷酶的活性 将检测葡萄糖-低聚糖-脂类。所有这些研究 可提供有关复合体的生物合成的信息 视网膜中的碳水化合物。

The carbohydrate chains of rhodopsin are unique as compared to other asparagine-linked glycoproteins, suggesting the presence of special mechanisms which control their biosynthesis. We wish to investigate this regulatory process. (1) We shall examine the possibility that the assembly of its oligosaccharides is influenced by signals encoded in the polypeptide backbone of opsin. A key step in the formation of the complex type of oligosaccharide chain would be the addition of a GlcNAc residue to the alpha (1- 6)-mannose arm of the major oligosaccharide of rhodopsin. What directs the retina not to have this structure on rhodopsin? (a) In order to explore the influence of the polypeptide on this reaction, we will examine the activity of purified GlcNAc-transferase II from rat liver as well as that of Golgi preparations from the retina using the purified oligosaccharide of rhodopsin as acceptor of GlcNAc, as compared to using opsin, rhodopsin, or glycopeptides which contain this same oligosaccharide. (b) We shall also examine the galactosylation of rhodopsin in the same manner. (c) We will alter the primary structure of opsin by incorporating amino acid analogs into the polypeptide and examine the effect of this alteration on the glycosylation of bovine rhodopsin. (2) We shall explore the Golgi of the retina for the presence of beta-galactosidase and exohexosaminidase activities using pertinent analogs of opsin as substrates. (3) We shall characterize the oligosaccharides of the processing intermediates involved in the glycosylation of rhodopsin. Pre- opsins synthesized in the inner segment region of the rod cell will be isolated by immunological techniques. The oligosaccharides will be liberated enzymatically, and their structures investigated. The effect of inhibitors of processing will aslo be examined. The techniques of analysis by HPLC, plus enzymatic and chemical processing will also be examined. The techniques of analysis by HPLC, plus enzymatic and chemical degradation, will be used in all of these studies. We shall continue our studies dealing with metabolic regulation of the dolichol pathway. Previously, we have shown that dolichol-P- mannose acts as an allosteric activator of the enzyme that catalyzes the first reaction of the pathway. We shall examine the influence of other intermediates of the dolichol pathway on the activating phenomenon. These investigations may reveal additional aspects of control for this key aspect of glycoprotein biosynthesis. The activity of glucosidases of the retina toward Glc-oligosaccharide-lipids will be examined. All of these studies may provide information concerning the biosynthesis of complex carbohydrates by the retina.