STRUCTURE AND FUNCTION OF ENZYMES INVOLVED IN THE METABOLISM OF POLYSIALIC ACID

多聚唾液酸是几种细菌的毒力因子， 脑膜炎 它也存在于发育中的人脑中。 这 常见沿着的免疫原性差， 多糖阻碍了其作为疫苗的用途。 需要几种酶 聚唾液酸生物合成也是唾液酸化 脊椎动物糖蛋白 该项目的目标是 表征这些酶的结构和功能， 作为了解细菌和人类唾液酸化的工具。 氨基酸序列与E.大肠杆菌CMP-唾液酸 合成酶，唾液酸化中的必需酶，具有 存在于其他病原菌中的酶表明是保守的氨基酸。 在氨基末端序列中已鉴定出几个碱性残基 通过定点突变作为E.大肠杆菌CMP-唾液酸 酸性合成酶 这些残基在所有已知的细菌中是保守的。 CMP-neuAc合成酶。 对E.大肠杆菌突变株 酶表明，这些残基可能发挥重要作用， 产物的形成和核苷酸底物的相互作用。 的 从牛垂体中纯化了同源酶 腺体

Polysialic acid is a virulence factor for several bacteria causing meningitis. It is alos present in the developing human brain. This common occurrence along with the poor immunogenicity of this polysaccharide hampers its use as a vaccine. Several enzymes required for the biosynthesis of polysialic acid are also required for sialylation of vertebrate glycoproteins. The objective of this project is to characterize the structure and function of these enzymes and the use of them as tools for understanding sialylation in bacteria and humans. Comparison of the amino acid sequence with of the E. coli CMP-sialic acid synthetase, an essential enzyme in sialylation, with sequences of the enzyme present in other pathogenic bacteria suggest conserved amino acids. Several basic residues have been identified in the amino terminal sequence by site directed mutagenesis as active residue in the E. coli CMP-sialic acid synthetase. These residues have are conserved in all known bacterial CMP-neuAc synthetase enzymes. Kinetic analysis of the E. coli mutant enzymes suggests these residues may play an essential role in the formation of product and the interaction of nucleotide substrate. The homologous enzyme has been purified to homogeniety from bovine pituitary glands.