DEOXYHEXOSE BIOSYNTHESIS

许多天然存在的抗生素和其他具有生物活性的微生物代谢物是糖苷，代表大量不同的苷元中的一种与一种或多种不寻常的糖，特别是脱氧和脱氧氨基己糖的结合。这些化合物中的糖成分通常对生物活性是绝对必要的。这些糖大部分是由D-葡萄糖在dTDP-己糖水平上合成的，然后通过糖基转移酶转移到苷元上。然而，除了最初的步骤外，我们对这些糖核苷酸转化所涉及的机制和酶的了解是有限的。这种有限的知识一直是在药物发现中有吸引力的应用的障碍，即相同的糖和苷元的非自然组合的组合生物合成。在拟议的项目中，我们计划通过用适当克隆的抗生素生物合成基因表达的重组酶重组代表dTDP-2-脱氧-、2，3-二脱氧-2，3-二脱氧-3-氨基和3，4-二脱氧-3-氨基-3-氨基己糖的糖核苷酸，并研究它们的形成机制，来加深我们对抗生素关键脱氧己糖成分形成的理解。这项工作将为组合酶法合成代表抗生素糖和苷元新组合的新的非天然糖苷奠定基础。

Many of the naturally occurring antibiotics and other biologically active microbial metabolites are glycosides, representing a combination of one of a large number of different aglycones with one or more of a number of unusual sugars, particularly deoxy- and deoxyaminohexoses. The sugar component in these compounds is usually absolutely essential for biological activity. Most of these sugar moieties are synthesized from D- glucose at the level of a dTDP-hexose and then transferred to the aglycone by a glycosyltransferase. Yet, except for the very initial steps, our knowledge of the mechanisms and enzymes involved in these sugar nucleotide transformations is limited. This limited knowledge has been an impediment to an attractive application in drug discovery, the combinatorial biosynthesis of unnatural assemblies of the same sugars and aglycones. In the proposed project we plan to enhance our understanding of the formation of key deoxyhexose components of antibiotics by reconstituting, with recombinant enzymes expressed from the appropriate cloned antibiotic biosynthesis genes, the enzymatic formation of sugar nucleotides representing dTDP-2-deoxy-, 2,3- dideoxy-, 2,3-dideoxy-3-amino-, and 3,4-dideoxy-3-aminohexoses and by studying the mechanisms of their formation. This work will lay one of the foundations for the combinatorial enzymatic synthesis of new, unnatural glycosides representing new combinations of antibiotic sugars and aglycones.