APPLICATION OF NMR TO THE STUDY OF XYLOSE SYNTHASES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 参与将UDP-GLCA转化为其他UDP-糖的酶在真核生物中得到了很好的描述，但在原核生物中知之甚少。在此，我们鉴定并鉴定了青枯雷尔氏菌的一个基因(RsU4kpxs)。GMI1000，编码双功能酶UDP-4-酮-戊糖/UDP-木糖合成酶(UXS)。一种是在NAD存在下将UDP-葡萄糖醛酸脱羧基生成UDP-L-苏糖-4“-酮-戊糖，第二种是将UDP-4-酮基-戊糖和NADH转化为UDP-木糖和NAD，虽然速率较低。对青枯病菌酶的鉴定使我们可以推测，在早期细菌中，祖先的UXS(以及UDP-APiose合成酶或UAXS)分化为两种不同的酶活性。这种分离产生了目前动物、真菌和植物中的UXS以及植物的UXS同源物。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The enzymes involved in converting UDP-GlcA to other UDP-sugars are well described in eukaryotes, but less is known in prokaryotes. Here we identify and characterize a gene (RsU4kpxs) from Ralstonia solanacearum str. GMI1000, which encodes a dual-function enzyme, UDP-4-keto-pentose/UDP-xylose synthase (UXS). One activity is to decarboxylate UDP-glucuronic acid to UDP-¿-L-threo-pentopyranosyl-4"-ulose (UDP-4-keto-pentose) in the presence of NAD+. The second converts UDP-4-keto-pentose and NADH to UDP-xylose and NAD+, albeit at a lower rate. The identification of the R. solanacearum enzyme enables us to propose that the ancestral UXS (as well as UDP-apiose synthase or UAXS) diverged into two distinct enzymatic activities in early bacteria. This separation gave rise to the current Uxs in animal, fungus and plant as well as to the plant Uaxs homologs.