X-ray Studies of Sugar-Modifying Enzymes

核苷酸连接糖存在于所有生物体中，它们在其中发挥着各种重要的生物学作用。 在半乳糖代谢中，这一直是该实验室十二年来的主要焦点之一，糖附着在UDP上。 有趣的是，许多脱氧糖显示出广泛的生物活性，从介导细胞-细胞相互作用到作为各种抗生素的组分，它们是通过生物化学途径合成的，从α-D-葡萄糖-1磷酸连接到CDP或TDP开始。这项资助更新的总体目标是通过X射线晶体学和定点诱变技术来了解特异性修饰核苷酸连接糖的酶的结构。将研究的系统包括人UDP-半乳糖4-差向异构酶、来自Y. pseudotuberculosis IVA、S.从S.委内瑞拉人参与了desosamine的生物合成。UDP-半乳糖4-差向异构酶通过催化UDP-半乳糖和UDP-葡萄糖的相互转化在半乳糖代谢中起作用。CDP-泰维糖。 泰维糖存在于某些类型的革兰氏阴性细菌的O-抗原中。 这些待研究的2，3-脱氢酶催化真菌糖生物合成的第一步。 真菌糖和氨基葡萄糖都是在一些大环内酯类抗生素如红霉素中发现的脱氧糖。 UDP-半乳糖4-差向异构酶的研究已进入最后阶段。 对涉及脱氧糖生物合成的酶的拟议研究是全新的。 最终，新的结构分析将产生详细的蛋白质：配体相互作用的三维描述，并可能最终提供一个分子基础上的新的抗菌剂的设计。

Nucleotide-linked sugars are found in all organisms where they fulfill a variety of important biological roles. In galactose metabolism, which has been one of the main focuses of this laboratory for twelve years, the sugar is attached to UDP. Interestingly, many of the deoxysugars, which display wide ranges of biological activities from mediating cell-cell interactions to serving as components in various antibiotics, are synthesized via biochemical pathways starting with the attachment of alpha-D-glucose-1 phosphate to either CDP or TDP. The overall goal of this grant renewal is to understand by x-ray crystallographic and site-directed mutagenesis techniques, the structures of enzymes that specific modify nucleotide-linked sugars. The systems that will be investigated include human UDP-galactose 4-epimerase, CDP-D-tyvelose 2-epimerase from Y. pseudotuberculosis IVA, 2,3-d4ehydratase from S. fradiae, and seven enzymes isolated from S. venezuelae that are involved in the biosynthesis of desosamine. UDP-galactose 4-epimerase functions in galactose metabolism by catalyzing the interconversion of UDP-galactose and UDP-glucose. CDP-tyvelose. Tyvelose occurs in the O-antigens of some types of gram-negative bacteria. These 2,3-dehydratase to be studied catalyzes the first step in mycarose biosynthesis. Both mycarose and desosamine are deoxysugars found in some macrolide antibiotics such as erythromycin. The research on UDP-galactose 4-epimerase is in its final stage. The proposed studies on enzymes involved deoxysugars biosynthesis are completely new. Ultimately new structural analysis will yield detailed three-dimensional descriptions of protein: ligand interactions and may eventually provide a molecular foundation upon which to base the design of new antimicrobial agents.