RELATION OF ENZYME PROCESSING TO HEPATIC GLUCURONIDATION

UDP-葡萄糖醛酸基转移酶(UDPGT)是一组 糖蛋白酶集中在内质网中 肝细胞，这是解毒所必需的 内部代谢物和外来物质，如药物， 致癌物质和环境毒素。UDPGT以几种形式存在 异构体；UDPGT特定形式的遗传缺陷导致 人和突变(Gunn)大鼠的终生黄疸。在预赛中 我们的研究表明，冈恩大鼠有大致正常的 两种功能缺陷的UDPGT亚型的数量。 然而，功能异质性的生化基础和 UDPGTS的遗传性功能障碍尚不清楚。这个 拟议项目的目的是确定可能的角色 糖基化和其他类型的共翻译和后翻译- 泛函生成中的翻译变化 UDPGT的异质性和遗传性功能缺陷。我们 计划开发符合以下条件的单抗和多克隆抗体 对单个UDPGT亚型的特异性并利用这些亚型来研究 UDPGT基因在近交系正常大鼠和近交系大鼠中的表达 同基因冈恩大鼠。不同UDPGT亚型的前体 将通过无细胞翻译来自于 正常大鼠；这些前体将与那些衍生的 通过翻译Gunn大鼠肝脏的mRNA。生物合成步骤 UDPGT前体的合成及其蛋白质和蛋白质的加工 碳水化合物的成分将通过代谢标记进行研究 Gunn大鼠及同种异体大鼠肝脏中肝细胞的分离 正常大鼠。由于UDPGT是完整的内质网 蛋白质，除了阐明生物化学基础外 这一重要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 一般为内质网蛋白。

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.