HYDROLYSIS OF VITAMIN A ESTERS IN LIVER

视黄酸酯的酶解是体内 总体而言，维生素A的动态平衡。尽管肝脏在人体内起着核心作用 维生素A代谢，我们对肝酶的了解 催化的视黄酸酯的水解是不完全的。只有一个这样的 酶已经以纯净的形式被分离出来，它是一种中性的、依赖于胆盐的酶 视黄酸酯水解酶(BSDREH)，这是最近才实现的。 这项建议的目的是获得关于以下方面的新的详细信息 视黄醇酯的功能、调节和生理作用 肝脏中的水解酶。这将提高对因素的基本理解 控制维生素A动态平衡。这些信息很重要，因为 维甲酸在血管生成和维持中的关键作用 分化的组织和维甲酸在预防 或治疗某些癌症。目的1比较肝脏BSDREH 和胰腺胆固醇酯水解酶在蛋白质水平 将制作结构、cDNA序列和酶性质，以便 检验肝酶和胰酶相同的假设 蛋白质或异构体。在目标2中，肝脏BSDREH的调节将是 通过检验酶合成低于 翻译控制和酶活性是由 翻译后修饰语。目标3胆盐非依赖性视黄醇 大鼠肝脏的酯水解酶将以纯净的形式分离出来，以便详细 对其生化和酶学性质进行了研究。AIM 4中的肝癌 细胞培养模型系统将被用来检验这样的假设 胆盐依赖和非胆盐非依赖性视黄酸酯水解酶的作用 肝脏维生素的一个或多个途径中的重要生理作用 新陈代谢。

The enzymatic hydrolysis of retinyl esters is a key process in the body's overall vitamin A homeostasis. Although the liver plays a central role in vitamin A metabolism, our understanding of the hepatic enzymes that catalyse the hydrolysis of retinyl esters is incomplete. Only one such enzyme has been isolated in pure form, a neutral, bile salt dependent retinyl ester hydrolase (BSDREH), and this has only been recently achieved. The objective of this proposal is to obtain new and detailed information on the functions, regulation, and physiological role of the retinol ester hydrolases in the liver. This will improve basic understanding of factors controlling vitamin A homeostasis. Such information is important given the critical role of retinoids in the development and maintenance of differentiated tissues and the roles that retinoids may play in preventing or treating certain cancers. In Aim 1 comparisons of the hepatic BSDREH and pancreatic cholesteryl ester hydrolase at the levels of protein structure, CDNA sequence, and enzyme properties will be made in order to test the hypothesis that the hepatic and pancreatic enzymes are the same protein or isoforms. In Aim 2 the regulation of the hepatic BSDREH will be probed by testing the hypothesis that enzyme synthesis is under translational control and that enzyme activity is regulated by postranslational modifications. In Aim 3 the bile salt-independent retinyl ester hydrolases of rat liver will be isolated in pure form for detailed study of their biochemical and enzymological properties. In Aim 4 hepatoma cell culture model systems will be used to test the hypothesis that the bile salt dependent and bile salt-independent retinyl ester hydrolases play physiologically important roles in one or more pathways of hepatic vitamin A metabolism.