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

9723593康韦Entner-Doudoroff通路(ED)在大量重要微生物中形成了中枢代谢的核心，分布广泛，包括最根深蒂固的古生菌。在大肠杆菌中，ED途径被诱导为葡萄糖酸分解代谢，以及两个葡萄糖酸运输和磷酸化系统。虽然人们普遍认识到，线虫已经进化到在肠道栖息地生长，但人们对所使用的营养物质知之甚少。最近的证据表明，葡萄糖酸通过ED途径的代谢对于大肠杆菌在大肠的定植是必不可少的。这个实验室的长期目标是了解ED途径在自然界中的作用以及在糖酵解途径的进化过程中的作用。我们已经开始利用基因组信息来研究参与葡萄糖酸代谢的四个葡萄糖酸转运体、两个葡萄糖酸激酶和两个调节蛋白。葡萄糖酸转运和磷酸化的GNTI系统包含两个转运蛋白基因：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生长的生理。葡萄糖尿酸，而不是葡萄糖酸，是另一种最近发现的葡萄糖酸转运蛋白基因的诱导信号。由于大肠中含有比葡萄糖酸更多的葡萄糖尿酸，而且葡萄糖尿酸诱导另一种糖酸的分解代谢途径，因此似乎葡萄糖尿酸在自然界中提供了糖酸可获得性的一般信号。葡萄糖醛酸诱导和GntP功能对葡萄糖酸盐生长的重要性正在被研究。葡萄糖酸转运和磷酸化的GNTII辅助系统(通常只有在没有GNTI系统的情况下才能发挥作用)还编码两种新发现的“脱氢酶类”酶，它们允许在L-爱奥酸上生长，葡萄糖酸是关键的中间体。GntII途径的生化和生理学正在研究中。由于葡萄糖酸似乎是GntII途径的中间体，而且葡萄糖酸是其他调节子的诱导者，从细胞经济的角度来看，在这些途径之间存在串扰似乎是重要的。一种既是GntII的正调节因子又是GNTI的负调节因子的蛋白质正在被鉴定。本项目的最终目的是阐明大肠杆菌对糖酸代谢的生理、生化和调控，以便更全面地了解其生态学。虽然人们普遍认识到，大肠杆菌已经进化到在肠道栖息地生长，但人们对哪些营养物质用于支持生长知之甚少。最近的证据表明，葡萄糖酸的代谢是大肠杆菌在大肠中定植所必需的，葡萄糖酸是葡萄糖的一种酸性形式。在大肠杆菌中，Entner-Doudoroff途径用于大肠中葡萄糖酸和其他糖酸的新陈代谢。在大肠杆菌中运行的Entner-Doudoroff途径是非常复杂的，至少有10个基因和3个水平的遗传调控参与糖酸代谢。本项目的目的是为了更全面地了解Entner-Doudoroff途径在大肠定植中的作用，对大肠杆菌的生理生化和糖酸代谢的调控进行研究。

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.