RELATION OF ENZYME PROCESSING TO HEPATIC GLUCURONIDATION

UDP-葡萄糖醛酸基转移酶（UDPGT）是一组 集中在内质网中的糖蛋白酶 肝细胞，这是必不可少的解毒， 内部代谢物和外来物质，例如药物， 致癌物质和环境毒素。 UDPGT有几种 异构体; UDPGT特定形式的遗传缺陷导致 人和突变型（古恩）大鼠的终身黄疸。 初步 我们的研究表明，古恩大鼠具有近似正常的 量的两种功能缺陷型UDPGT同种型。 然而，功能异质性的生化基础和 UDPGTs的遗传性功能障碍是未知的。 的 拟议项目的目的是确定可能的作用 糖基化和其他类型的共翻译和后 在功能生成中的翻译变化 UDPGT的异质性和遗传性功能缺陷。 我们 计划开发单克隆和多克隆抗体， 特异于单个UDPGT亚型，并使用这些来研究 UDPGT基因在近交系正常大鼠中的表达， 同种古恩大鼠。 单个UDPGT亚型的前体 将通过肝脏mRNA的无细胞翻译来鉴定， 正常大鼠;这些前体将与衍生的前体进行比较。 通过古恩大鼠肝脏mRNA的翻译。 生物合成步骤 UDPGT前体的合成及其蛋白质的加工， 碳水化合物组分将通过代谢标记进行研究， 从古恩大鼠和同种异体大鼠的肝脏中分离肝细胞， 正常老鼠 由于UDPGTs是内质网的组成部分， 蛋白质，除了阐明的生化基础， 这种基本酶系统的遗传性疾病，这些研究 可能有助于我们了解肝脏的组装机制 内质网蛋白。

UDP-glucuronosyltransferases (UDPGTs) are a group of glycoprotein enzymes concentrated in the endoplasmic reticulum of liver cells, which are essential for the detoxification of internal metabolites and foreign substances, e.g. drugs, carcinogens and environmental toxins. UDPGTs exist as several isoforms; inherited defects of specific forms of UDPGT result in life-long jaundice in man and mutant (Gunn) rats. In preliminary studies we have shown that Gunn rats have approximately normal amounts of two functionally defective UDPGT isoforms. However, the biochemical basis of functional heterogeneity and inherited functional disorders of UDPGTs is not known. The purpose of the proposed project is to determine the possible role of glycosylation and other types of co-translational and post- translational changes in the generation of functional heterogeneity and inherited functional defects of UDPGTs. We plan to develop monoclonal and polyclonal antibodies that are specific for individual UDPGT isoforms and to use these to study the expression of UDPGT genes in inbred normal rats and congeneic Gunn rats. Precursors of individual UDPGT isoforms will be identified by cell-free translation of liver mRNA from normal rats; these precursors will be compared with those derived by translation of Gunn rat liver mRNA. Biosynthetic steps of synthesis of UDPGT precursors and processing of their protein and carbohydrate components will be studied by metabolic labeling of hepatocytes isolated from livers of Gunn rats and congeneic normal rats. Since UDPGTs are integral endoplasmic reticulum proteins, in addition to elucidation of the biochemical basis of inherited disorders of this essential enzyme system, these studies may help us understand the mechanism of assembly of liver endoplasmic reticulum proteins in general.