BIOLOGY OF SIALIC ACID SUBSTITUTIONS

许多特定的生物功能被归因于 唾液酸。然而，大多数对唾液酸的研究都没有考虑到 考虑到母体分子的修饰所产生的多样性， 例如侧链的0-乙酰化。在之前的资助期间 期间，我们开发了新的、灵敏的方法来分析 修饰的唾液酸，发现了一些新的和意想不到的分子， 研究了来自E.Coli、大鼠肝脏和 人黑色素瘤，已鉴定并表征为唾液酸特异性 0-乙酰基酯酶，研究了其生物合成和周转 N-羟基唾液酸，并发现了一种新的 黑色素瘤神经节苷脂中的去-N-乙酰化/再-N-乙酰化反应。 最近，我们开发了一种新的方法来废除 O-乙酰化在小鼠早期胚胎和选定的小鼠组织中的表达 转基因小鼠。在即将到来的资助期，我们将集中我们的 请注意以下事项： 1.大鼠肝脏的纯化、重组及其特性 唾液酸O-乙酰转移酶(S)。 2.O-乙酰化唾液酸的亚细胞分布 大鼠肝脏中的酶。 3.人黑色素瘤唾液酸的纯化、重组及性质 酸性O-乙酰转移酶(S)。 4.唾液酸脱-N-乙酰化和再-N-乙酰化反应机理 神经节苷脂。 5.唾液酸特异性编码基因的分子克隆 O-乙酰转移酶(S)。 6.取消小鼠胚胎早期的O-乙酰化。 7.在转基因小鼠的选定组织中取消O-乙酰化。 从长远来看，这些研究将帮助我们理解 唾液酸及其修饰在健康和卫生中的生物学作用 疾病。到目前为止，我们的发现表明，这些分子与多种 重要作用，包括保护粘膜免受微生物的伤害 表面，补体激活的调节，表达 多种肿瘤中的癌胎儿抗原及其细胞-细胞调控 在某些器官发育过程中的相互作用。

Many specific biological functions have been attributed to sialic acids. However, most studies of sialic acids do not take into account the diversity generated by modifications of the parent molecule, such as 0-acetylation of the side chain. During the prior funding period, we have developed new and sensitive methods for the analysis of modified sialic acids, identified some new and unexpected molecules, studied sialic acid:O-acetyltransferases from E.Coli., rat liver and human melanoma, identified and characterized sialic acid-specific 0-acetyl-esterases, studied the biosynthesis and turnover of the N-glycolyl group of sialic acids, and discovered a novel de-N-acetylation/re-N-acetylation reaction in melanoma gangliosides. Most recently, we have developed a novel approach to abrogate O-acetylation in the early mouse embryo, and in selected tissues of transgenic mice. In the upcoming grant period, we will focus our attention upon the following: 1. Purification, reconstitution and characterization of the rat liver Sialic Acid O-acetyltransferase(s). 2. Subcellular distribution of O-acetylated sialic acids, and the related enzymes in rat liver. 3. Purification, reconstitution and properties of human melanoma Sialic Acid O-acetyltransferase(s). 4. Mechanisms for de-N-acetylation and re-N-acetylation of sialic acids on gangliosides. 5. Molecular cloning of cDNAs encoding sialic acid specific O-acetyltransferase(s). 6. Abrogation of O-acetylation in the early mouse embryo. 7. Abrogation of O-acetylation in selected tissues of transgenic mice. In the long run, these studies will help us to understand the biological roles of sialic acids and their modifications in health and disease. Our findings to date implicate these molecules in a variety of important roles, including protection from microbial organisms on mucosal surfaces, the modulation of complement activation, the expression of oncofetal antigens in various tumors, and the regulation of cell-cell interaction during the development of certain organs.