Acetone metabolism in Helicobacter pylori

描述（申请人提供）：幽门螺杆菌是一种主要的人类病原体，定植于胃粘膜，导致胃炎症，可发展为慢性胃炎、消化性溃疡、胃癌或粘膜相关淋巴瘤。幽门螺杆菌在人胃中建立慢性感染的能力表明，它很好地适应了在这种独特的环境中获取生长所需的营养。两个不相关的幽门螺杆菌菌株26695和J99的完整基因组序列极大地帮助了对这种细菌生理学的理解。据报道，这两种测序菌株最近都含有一种潜在的丙酮羧化酶的基因，这种酶通过将丙酮转化为乙酰乙酸来启动丙酮的代谢。丙酮在体内是由乙酰乙酸自发脱羧产生的，乙酰乙酸是由肝脏产生的酮体之一，当葡萄糖不容易获得时用作能量来源。酮总是存在于血液中，一个健康成年人的肝脏每天产生185克酮体。这一提议将验证幽门螺旋杆菌利用丙酮作为胃粘膜细菌重要能量来源的假设。该提案的第一个具体目标是通过在大肠杆菌中表达该蛋白，纯化该蛋白并检查其催化丙酮羧化的能力来验证幽门螺杆菌具有功能性丙酮羧化酶。第二个具体目的是确定幽门螺杆菌是否需要这种酶来建立胃粘膜的慢性感染。编码幽门螺杆菌丙酮羧化酶的操纵子将被破坏，由此产生的突变菌株将被检查其在小鼠和蒙古沙鼠胃中定植的能力。所提出的研究将扩大对幽门螺杆菌代谢途径的认识，这将有助于更好地了解这种病原体如何在人类中建立感染，并可能为预防或治疗幽门螺杆菌感染提供新的策略。

DESCRIPTION (provided by applicant): Helicobacter pylori is a major human pathogen that colonizes the gastric mucosa, leading to gastric inflammation that can progress to chronic gastritis, peptic ulcer, gastric cancer or mucosal-associated lymphoma. The ability of H. pylori to establish a chronic infection in the human stomach indicates that it is well adapted to acquire the nutrients it needs for growth in this unique environment. Complete genomic sequences for two unrelated H. pylori strains, 26695 and J99, have greatly aided the understanding of the physiology of this bacterium. Both sequenced strains were reported recently to have the genes for a potential acetone carboxylase, an enzyme that initiates the metabolism of acetone by converting it to acetoacetate. Acetone is produced in the body upon the spontaneous decarboxylation of acetoacetate, one of the ketone bodies produced by the liver and used as an energy source when glucose is not readily available. Ketones are always present in the blood, with up to 185 grams of ketone bodies produced per day by the liver of a healthy adult. This proposal will test the hypothesis that H. pylori utilizes acetone as an important energy source for the bacterium in the gastric mucosa. The first specific aim of the proposal is to verify that H. pylori has a functional acetone carboxylase by expressing the protein in Escherichia coli, purifying it, and examining its ability to catalyze the carboxylation of acetone. The second specific aim is to determine if this enzyme is needed by H. pylori to establish a chronic infection in the gastric mucosa. The operon encoding the H. pylori acetone carboxylase will be disrupted and the resulting mutant strain will be examined for its ability to colonize the stomachs of mice and Mongolian gerbils. The proposed studies will expand knowledge of metabolic pathways in H. pylori, which will lead to a better understanding of how this pathogen establishes infections in humans and may provide new strategies for the prevention or treatment of H. pylori infections.