HYDROLYSIS OF VITAMIN A ESTERS IN LIVER

视黄酯的酶水解是体内的关键过程 整体维生素 A 稳态。 虽然肝脏在其中起着核心作用 维生素 A 代谢，我们对肝酶的理解 催化视黄酯的水解不完全。 只有这样一个 酶已以纯品形式分离出来，是一种中性、胆汁盐依赖性的酶 视黄酯水解酶（BSDREH），这是最近才实现的。 该提案的目的是获取有关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 体内平衡。 鉴于以下情况，此类信息很重要 类维生素A在发育和维持中的关键作用 分化的组织以及类维生素A在预防中可能发挥的作用 或治疗某些癌症。 目标 1 肝脏 BSDREH 的比较 和蛋白质水平的胰腺胆固醇酯水解酶 结构、cDNA 序列和酶特性将被确定，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 通过检验酶合成受到影响的假设来探讨 翻译控制和酶活性受调节 翻译后修饰。 在目标 3 中，不依赖胆汁盐的视黄基 大鼠肝脏的酯水解酶将以纯形式分离，用于详细研究 研究它们的生化和酶学特性。 目标 4 肝癌 细胞培养模型系统将用于检验以下假设： 胆汁盐依赖性和胆汁盐非依赖性视黄酯水解酶发挥作用 在肝脏维生素的一种或多种途径中具有重要的生理作用 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.