Synthesis and function of novel bacterial carbohydrates

糖组代表了基因组、转录组和蛋白质组之上的额外信息层，破译其作用是一个基本问题。这个问题在产生多种多样的非均匀组成的聚糖的细菌中特别重要。阐明它们的生物合成将允许评估它们的功能并利用新型糖合成酶的潜力用于生物技术应用。我们专注于从弯曲杆菌或耶尔森氏菌修饰的庚糖，其特征在于9庚糖修饰酶，影响胶囊和脂多糖的功能，其中修饰的庚糖驻留。我们的研究表明，C.空肠具有非常精确底物和产物特异性。 目前的建议侧重于了解这种特异性的分子基础，并阐明新的甲基转移酶和氧化酶在庚糖修饰的功能。我们的工作还强调了一个新的假定的调节器内的C。空肠囊簇，也表明与其他聚糖的合成的胶囊合成的共调节。阐明所涉及的机制可以更好地描述每个通路的生理作用，并了解它们在生理条件下如何整合。 我们假设：（i）参与庚糖修饰的还原酶和差向异构酶具有独特的底物/产物特异性，可用于生物技术应用;（ii）新的推定甲基转移酶和专用氧化酶参与庚糖修饰;（iii）新的调节剂调节庚糖修饰、胶囊合成和其他表面碳水化合物。 我们的具体目标是：*1/研究庚糖修饰差向异构酶和还原酶的底物/产物特异性的分子基础。2/确定推定的甲基转移酶、氧化酶和调节剂对庚糖修饰和胶囊和其他表面碳水化合物的产生的作用。 这项研究具有普遍意义，因为在许多细菌的表面碳水化合物中发现了修饰的庚糖和其他不寻常的糖。从我们的结构/功能的底物和产品特异性的决定因素的研究中获得的信息将有助于阐明其他细菌糖的合成途径。这项研究还将阐明糖合成的调控机制，以更好地了解糖合成途径之间的相互作用及其对细菌生理的影响。最后，这项研究将提供底物，使糖基转移酶的研究参与组装复杂的碳水化合物结构。这可能导致庚糖修饰酶在生产复杂碳水化合物方面的技术应用。

The glycome represents an extra layer of information above the genome, transcriptome and proteome and deciphering its role is a fundamental question. This question is particularly important in bacteria that produce a wide variety of glycans of heterogeneous composition. Elucidating their biosynthesis will allow assessing their function and harnessing the potential of novel sugar synthesis enzymes for biotechnology applications. We focused on modified heptoses from Campylobacters or Yersiniae and characterized 9 heptose modification enzymes that affect the function of the capsule and lipopolysaccharide in which the modified heptoses reside. Our work showed that heptose modifying reductases and epimerases from C. jejuni have very precise substrate and product specificities.*** The current proposal focuses on understanding the molecular basis of such specificity, and on elucidating the function of new methyltransferases and oxidases in heptose modification. Our work also highlighted a novel putative regulator within the C. jejuni capsular cluster, and also suggests co-regulation of capsule synthesis with the synthesis of other glycans. Elucidating the mechanisms involved may allow to better delineate the physiological role of each pathway and understand how they are integrated under physiological conditions.*** We hypothesize that: (i) the reductases and epimerases involved in heptose modification have unique substrate / product specificities that can be exploited for biotechnological applications; (ii) novel putative methyl-transferases and a dedicated oxidase are involved in heptose modification and (iii) a novel regulator regulates heptose modification, capsule synthesis, and other surface carbohydrates.*** Our specific objectives are to:***1/ investigate the molecular basis for substrate / product specificities of heptose modifying epimerases and reductases.***2/ determine the role of putative methyltransferases, oxidase and regulator on heptose modification and production of capsule and other surface carbohydrates.*** The proposed research is of general significance as modified heptoses and other unusual sugars are found in surface carbohydrates of numerous bacteria. The information derived from our structure / function studies on determinants for substrate and product specificities will facilitate the elucidation of the synthesis pathways for other bacterial sugars. This research will also delineate regulatory mechanism involved in sugar synthesis to better understand the interplay between sugar synthesis pathways and their effect on bacterial physiology. Finally, this research will provide substrates enabling the studies of glycosyltransferases involved in the assembly of complex carbohydrate structures. This could lead to technological applications of heptose modifying enzymes for the production of complex carbohydrates.********