The Chemistry and Biology of Galactofuranose Residues

描述(由申请人提供)：半乳呋喃糖(Galf)残留物与许多微生物的毒力或生存能力有关，包括分枝杆菌。这项拟议研究的目标是了解Galf残基掺入分枝杆菌细胞壁的机制。我们将研究这一过程中的两个关键酶的结构、催化机理和功能：黄素酶尿苷-5‘-二磷酸(UDP)-半乳糖基吡喃葡萄糖变位酶(GLF或UGM)和半乳糖基呋喃糖基转移酶GlfT2。这个应用程序的三个具体目标如下。目的1了解黄素酶UGM的作用机制。阐明UGM的催化机制将加深我们对黄素酶的各种化学成分的理解，有助于深入了解细胞壁生物合成的化学基础，并指导这一关键酶的抑制剂的产生。目标2是开发有效的、可穿透细胞的UGM抑制剂，可作为细胞壁生物合成的探针，并作为开发新的抗分枝杆菌药物的先导。目的3研究GlfT2酶，该酶催化1，5-和1，6-Galf残基交替连接的半乳聚糖聚合物的合成。我们将测试聚合是否是过程的，探索单个酶如何产生两个区域异构体糖键，并确定如何控制聚合物长度。这些研究将阐明分枝杆菌中半乳糖生物合成的机制，以及多糖类的生物合成。在追求这些目标的过程中，我们将采用有机化学、糖生物学、碳水化合物化学、化学酶学、结构生物学、微生物学和化学生物学的方法和思想。意义：拟议的研究结果将为半乳聚糖聚合物的组装提供新的见解，半乳聚糖聚合物是分枝杆菌细胞壁的重要组成部分。他们还将解决一个基本问题，即在没有模板的情况下，生物系统如何控制聚合物长度。这些知识将被应用于开发阻止分枝杆菌细胞生长的小分子。这些药物将成为分枝杆菌细胞壁生物合成的有价值的探针，并成为开发新的抗分枝杆菌药物的先导。

DESCRIPTION (provided by applicant): Galactofuranose (Galf) residues have been implicated in the virulence or viability of many microbes, including mycobacteria. The goal of the proposed research is to understand the mechanisms underlying Galf residue incorporation into the mycobacterial cell wall. We shall investigate the structure, catalytic mechanism, and function of two key enzymes in this process: the flavoenzyme uridine-5'-diphosphate (UDP)-galactopyranose mutase (Glf or UGM) and the galactosylfuranosyltransferase GlfT2. The three Specific Aims of this application follow. Aim 1 is to understand the mechanism of the flavoenzyme UGM. Elucidating the catalytic mechanism UGM will enhance our understanding of the diverse chemistry of the flavoenzymes, provide insight into the chemistry underlying cell wall biosynthesis, and guide the generation of inhibitors of this essential enzyme. Aim 2 is to generate potent and cell-permeable inhibitors of UGM that can be used as probes of cell wall biosynthesis and as leads for the development of new antimycobacterial agents. Aim 3 is to investigate the enzyme GlfT2, which catalyzes the synthesis of a galactan polymer composed of alternating 1,5- and 1,6-linked Galf residues. We shall test whether the polymerization is processive, explore how a single enzyme generates two regioisomeric sugar linkages, and determine how polymer length is controlled. These investigations will illuminate the mechanisms underlying galactan biosynthesis in mycobacteria and the biosynthesis of polysaccharides, in general. In pursuing these Aims, we shall employ methods and ideas from organic chemistry, glycobiology, carbohydrate chemistry, chemical enzymology, structural biology, microbiology, and chemical biology. Significance: The results of the proposed research will provide new insights into the assembly of the galactan polymer, an essential component of the mycobacterial cell wall. They also will address the fundamental question of how biological systems control polymer length in the absence of a template. This knowledge will be applied to develop small molecules that block mycobacterial cell growth. Such agents will serve as valuable probes of mycobacterial cell wall biosynthesis and as leads for the development of new antimycobacterial drugs.