Urease Activity and Nitrogen Assimilation in Helicobacter pylori

幽门螺杆菌的脲酶活性和氮同化

基本信息

批准号：
8367291
负责人：
Erica Francesca Miller
金额：
$ 3.09万
依托单位：
UNIVERSITY OF GEORGIA
依托单位国家：
美国
项目类别：
财政年份：
2011
资助国家：
美国
起止时间：
2011-08-23 至 2013-08-22
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8367291
关键词：
Acclimatization Accounting Acidity Acids Address Amino Acids Ammonia Ammonium Anemia Assimilations Bacillus subtilis Bacteria Bacterial Physiology Belief Biochemical Buffers Carbon Dioxide Carcinogens Cells Childhood Crowding Duodenal Ulcer Economic Conditions Enterobacter aerogenes bacterium Environment Enzymes Epithelial Cells Gastric ulcer Gastritis Genome Genomics Glutamate Dehydrogenase Glutamate-Ammonia Ligase Heart Helicobacter Infections Helicobacter pylori Homologous Gene Hydrolysis In Vitro Infection Kinetics Life Metabolism Methods Molecular Mutagenesis Nitrogen Nutrient Organism Outcome Pathogenesis Pathway interactions Peptic Ulcer Population Property Proteins Proteobacteria Protons Regulation Research Research Training Resistance Role Stomach Structure Surface System Taxon Techniques United States Urea Urea Nitrogen Urease cell motility in vivo killings lens malignant stomach neoplasm nitrogen metabolism novel periplasm

项目摘要

DESCRIPTION (provided by applicant): Discovered in the early 1980's, Helicobacter pylori is a common cause of peptic and duodenal ulcers, gastritis, anemia, and certain gastric cancers. This bacterium is typically acquired during childhood, with crowded living conditions and economic disparities closely correlating with higher infection rates. Urease is an enzyme that is required for infection by H. pylori, and accounts for nearly 10% of the total cellular protein. This enzyme must be active in order for the bacterium to colonize its host, a fact that has been explained by urease's ability to neutralize and buffer against the acidity of the stomach. However, the requirement for urease in colonization is not contingent upon acidic conditions, indicating alternative roles for this enzyme other than simply acid resistance. The primary objective of this research plan is to examine one of these alternative roles for urease-its role in nitrogen metabolism. Over the past fifteen years, two crucial turning points in urease research established this enzyme as player in nitrogen metabolism. First, a set of discoveries led to the current paradigm that urease is an intracellular enzyme, contrary to previously held beliefs. Secondly, urea nitrogen was shown to be incorporated into the cell through tracing studies of 15N-urea. High concentrations of urea have furthermore been shown to kill H. pylori, an effect that was explained by the hydrolysis of urea and subsequent accumulation of ammonium in the cell. The mechanism by which urea nitrogen is assimilated has been scarcely examined through biochemical methods; however, preliminary genome-level comparisons revealed that the pathway of ammonium assimilation in H. pylori is not typical of other proteobacteria. In fact, H. pylori is an anomaly among all other well-studied bacterial taxa with regard to both the structure and the regulation of the enzymes thought to assimilate ammonium in this organism-glutamine synthetase and glutamate dehydrogenase. Furthermore, glutamine synthetase is a putative interacting partner with urease, alluding to a potentially tight relationship between urease and ammonium assimilation. Using molecular techniques such as mutagenesis, in conjunction with biochemical techniques such as enzyme purification and kinetic studies, this study aims to characterize the pathway that takes urea from the gastric mileu directly to the heart of H. pylori primary metabolism.

描述（由申请人提供）：幽门螺杆菌于 20 世纪 80 年代初被发现，是消化性溃疡和十二指肠溃疡、胃炎、贫血和某些胃癌的常见原因。这种细菌通常是在儿童时期感染的，拥挤的生活条件和经济差距与较高的感染率密切相关。脲酶是幽门螺杆菌感染所需的一种酶，占细胞总蛋白的近10%。这种酶必须具有活性，细菌才能在其宿主中定殖，这一事实可以通过脲酶中和和缓冲胃酸的能力来解释。然而，定殖中对脲酶的需求并不取决于酸性条件，这表明该酶除了简单的耐酸性之外还有其他作用。该研究计划的主要目的是研究脲酶的替代作用之一——它在氮代谢中的作用。在过去的十五年里，脲酶研究的两个关键转折点确立了这种酶在氮代谢中的作用。首先，一系列发现导致了当前的范式，即脲酶是一种细胞内酶，这与以前的看法相反。其次，通过15N-尿素的示踪研究表明尿素氮被纳入细胞中。此外，高浓度的尿素已被证明可以杀死幽门螺杆菌，这种作用可以通过尿素的水解和随后细胞中铵的积累来解释。尿素氮同化的机制几乎没有通过生化方法进行研究。然而，初步的基因组水平比较表明，幽门螺杆菌中的铵同化途径并不是其他变形菌的典型途径。事实上，就被认为在该生物体中同化铵的酶（谷氨酰胺合成酶和谷氨酸脱氢酶）的结构和调节而言，幽门螺杆菌是所有其他经过充分研究的细菌类群中的一个异常。此外，谷氨酰胺合成酶是公认的脲酶相互作用伙伴，暗示脲酶和铵同化之间潜在的紧密关系。本研究旨在利用诱变等分子技术，结合酶纯化和动力学研究等生化技术，表征将尿素从胃部环境直接输送到幽门螺杆菌初级代谢核心的途径。