APPLICATION OF NMR TO THE STUDY OF XYLOSE SYNTHASES

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 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-苏式-4“-酮-戊糖，另一种是将UDP-4-酮基-戊糖和NADH转化为UDP-木糖和NAD+，虽然速率较低。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。这种分离导致了动物、真菌和植物中的UXS和植物的UXS同源物的产生。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. 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.