Physiology, Biochemistry and Molecular Genetics of Entner- Doudoroff Metabolism in Escherichia coli

endner - doudoroffpathway （ED）在大量重要微生物中构成中枢代谢的核心，分布广泛，包括最根深蒂固的古菌。在大肠杆菌中，ED途径被诱导用于葡萄糖酸盐分解代谢，以及葡萄糖酸盐转运和磷酸化两个系统。虽然人们普遍认为螺旋螺旋体已经进化到在肠道栖息地生长，但人们对哪种营养物质被使用知之甚少。最近的证据表明，通过ED途径的葡萄糖酸盐代谢是大肠杆菌定植大肠的必要条件。本实验室的长期目标是了解ED途径在自然界和糖酵解途径进化过程中的作用。我们已经开始利用基因组信息来研究参与葡萄糖代谢的四种葡萄糖转运蛋白、两种葡萄糖激酶和两种调节蛋白。葡萄糖酸盐转运和磷酸化的GntI系统包含两个转运基因，gntT和gntU。这项工作解决了这些转运蛋白的差异表达如何影响葡萄糖酸盐生长的生理。葡萄糖醛酸盐，而不是葡萄糖酸盐，信号诱导gntP，另一个最近发现的葡萄糖酸转运基因。由于大肠中葡萄糖醛酸盐比葡萄糖醛酸盐含有更多的葡萄糖醛酸盐，并且葡萄糖醛酸盐诱导另一种糖酸的分解代谢途径，因此葡萄糖醛酸盐似乎提供了自然界中糖酸可用性的一般信号。葡萄糖酸盐诱导和GntP功能对葡萄糖酸盐生长的重要性正在研究中。用于葡萄糖酸运输和磷酸化的GntII附属系统（通常仅在没有GntI系统的情况下起作用）也编码两种新发现的“脱氢酶样”酶，这些酶允许L-idonic酸生长，葡萄糖酸作为关键中间体。目前正在研究GntII通路的生物化学和生理学。由于葡萄糖酸盐似乎是GntII途径的中间体，并且葡萄糖酸盐是其他调控的诱导剂，因此从细胞经济的角度来看，这些途径之间的串扰似乎很重要。一种蛋白质，既是GntII的正调节和GntII的负调节被表征。该项目的最终目的是阐明大肠杆菌的生理生化和糖酸代谢调控，从而更全面地了解其生态学。虽然人们普遍认为大肠杆菌已经进化到可以在肠道栖息地生长，但人们对使用哪些营养物质来支持生长知之甚少。最近的证据表明，葡萄糖酸盐（葡萄糖的一种酸性形式）的代谢是螺旋杆菌在大肠中定植的必要条件。在E. coil中，enterner - doudoroff通路用于在大肠中发现的葡萄糖酸和其他糖酸的代谢。enterner - doudoroff通路，在大肠杆菌中起作用，非常复杂；至少有十个基因和三个层次的基因调控参与糖酸代谢。本项目的目的是表征大肠杆菌的生理生化和糖酸代谢调控，以便更全面地了解enterner - doudoroff通路在大肠定植中的作用。

9723593 Conway The Entner-Doudoroffpathway (ED) forms the core of central metabolism in a large number of important microorganisms and is widely distributed, including the most deeply rooted Archae. In E. coli, the ED pathway is induced for gluconate catabolism, together with two systems for gluconate transport and phosphorylation. While it is generally appreciated that E. coil has evolved to grow in the intestinal habitat, little is known about which nutrients are used. Recent evidence suggests that metabolism of gluconate via the ED pathway is essential for E. coli to colonize the large intestine. The long term goal of this laboratory is to understand the roles of the ED pathway in nature and during the course of evolution of glycolytic pathways. We have begun to employ genomic information to study the four gluconate transporters, two gluconate kinases, and two regulatory proteins involved in gluconate metabolism. The GntI system for gluconate transport and phosphorylation contains two transporter genes, gntT and gntU. The work addresses how differential expression of these transporters impacts the physiology of growth on gluconate. Glucuronate, not gluconate, signals induction of gntP, another recently discovered gluconate transporter gene. Since the large intestine contains more glucuronate than gluconate, and since glucuronate induces the catabolic pathway for yet another sugar acid, it appears that glucuronate provides a general signal of sugar acid availability in nature. The importance of glucuronate-induction and GntP function for growth on gluconate is being investigated. The GntII subsidiary system for gluconate transport and phosphorylation (which normally functions only in the absence of the GntI system) also encodes two newly identified "dehydrogenase-like" enzymes which allow growth on L-idonic acid, with gluconate as a key intermediate. The biochemistry and physiology of the GntII pathway is being studied. Since gluconate appears to be an intermediate of the GntII pathway, and since gluconate is an inducer of other regulons, it seems important in terms of cellular economy to have crosstalk between these pathways. A protein that is both a positive regulator of GntII and a negative regulator of GntI is being characterized. The ultimate goal of this project is to elucidate the physiology, biochemistry and, regulation of sugar acid metabolism by E. coli in order to more fully understand its ecology. While it is generally appreciated that E.coli has evolved to grow in the intestinal habitat, little is known about which nutrients are used to support growth. Recent evidence suggests that metabolism of gluconate, an acidic form of the sugar glucose, is essential for E. coil to colonize the large intestine. In E. coil, the Entner-Doudoroff pathway is used for metabolism of gluconate and other sugar acids that are found in the large intestine. The Entner-Doudoroff pathway, as it operates in E. coli, is very complex; there are at least ten genes and three levels of genetic regulation involved in sugar acid metabolism. The goal of this project is to characterize the physiology, biochemistry and, regulation of sugar acid metabolism by E. coli in order to more fully understand the role of the Entner-Doudoroff pathway in colonization of the large intestine.