Homocysteine & Heme: A Role in Thrombosis?

同型半胱氨酸

基本信息

批准号：
7548146
负责人：
Judith N Burstyn
金额：
$ 37.05万
依托单位：
UNIVERSITY OF COLORADO DENVER
依托单位国家：
美国
项目类别：
财政年份：
2000
资助国家：
美国
起止时间：
2000-09-05 至 2012-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7548146
关键词：
Active Sites Behavior Binding Biochemical Biochemistry Blood Blood Clot Blood Vessels Blood coagulation C-terminal Cataloging Catalogs Characteristics Chemistry Collaborations Cystathionine Cystathionine beta-Synthase Cysteine Defect Environment Enzymes Eukaryota Evolution Gene Proteins Genes Glutathione Goals Heme Hemeproteins Homocysteine Homocystine Homocystinuria Human Hydrogen Bonding Inherited Learning Link Metabolic Diseases Metabolism Methods Molecular Biology Molecular Genetics Mutation Names Occupations Outcome Study Patients Physiological Physiology Positioning Attribute Predisposition Production Property Protein Region Proteins Pyridoxal Phosphate Reaction Regulation Risk Role S-Adenosylmethionine Seminal Spectrum Analysis Stroke Sulfur Metabolism Pathway Symptoms Testing Thromboembolism Thrombosis Variant Work cofactor enzyme activity experience novel polypeptide premature protein folding protein function protein structure function response

项目摘要

DESCRIPTION (provided by applicant): Why is heme present in mammalian cystathionine beta-synthase (CBS)? Human CBS is a remarkable enzyme that requires three different cofactors: S-adenosylmethionine (AdoMet), heme and pyridoxal 5'-phosphate (PLP). Enzyme activity is regulated by AdoMet, which binds to the autoinhibitory C-terminal domain and opens the active site. The reaction chemistry of CBS is attributed solely to the PLP. The heme is essential for maximal enzyme activity but its precise role is as yet unclear. Positioned at a branch point in sulfur metabolism, CBS is the only enzyme that irreversibly removes toxic homocysteine from the body. A defect in the CBS protein in humans is the most common cause of homocystinuria, an inherited metabolic disease characterized by elevated levels of homocysteine and decreased levels of cysteine and glutathione and a profoundly enhanced risk of thromboembolism and stroke. More than one hundred pathological variants of CBS are known in homocystinuric patients, many of which cluster in the AdoMet-associated and heme-associated regions of the protein. We will investigate the biochemical consequences of the absence of heme and of select mutations in the AdoMet- and heme-binding regions of CBS, in order to determine how the three cofactors interact in the physiological function of the enzyme. This project is an integrated, collaborative effort between the Kraus lab, with expertise in the physiology and molecular genetics of homocysteine metabolism, and the Burstyn lab, with expertise in heme protein structure and function. To accomplish our goal we will combine physiological, biochemical, and biophysical methods to understand the role of heme in CBS. The Specific Aims for the continuation of this project are: 1) to test the hypothesis that the heme is critical for AdoMet regulation and functional stability of the human CBS protein, 2) to test the hypothesis that impaired AdoMet response correlates with aberrant behavior of heme or PLP, and 3) to test the hypothesis that the CBS heme stabilizes the active site PLP and that disruption of this interaction compromises CBS function.NARRATIVE Some people have errors in the gene for an important protein, named CBS, whose job is to remove the molecule homocysteine from blood. These people are very likely to get blood clots or have strokes because their CBS protein does not work properly and their homocysteine levels are too high. This project looks at the errors in the CBS protein, and tries to learn from those errors how the protein normally works.

描述（由申请人提供）：为什么哺乳动物的胱硫醚β-合酶 (CBS) 中含有血红素？人类 CBS 是一种非凡的酶，需要三种不同的辅因子：S-腺苷甲硫氨酸 (AdoMet)、血红素和 5'-磷酸吡哆醛 (PLP)。酶活性由 AdoMet 调节，AdoMet 与自抑制 C 末端结构域结合并打开活性位点。 CBS 的反应化学完全归因于 PLP。血红素对于最大酶活性至关重要，但其确切作用尚不清楚。 CBS 位于硫代谢的分支点，是唯一能不可逆地清除体内有毒同型半胱氨酸的酶。人类 CBS 蛋白缺陷是同型半胱氨酸尿症的最常见原因，同型半胱氨酸尿症是一种遗传性代谢疾病，其特征是同型半胱氨酸水平升高、半胱氨酸和谷胱甘肽水平降低，以及血栓栓塞和中风的风险大大增加。在同型半胱氨酸尿症患者中已知有一百多种 CBS 病理变异，其中许多聚集在该蛋白的 AdoMet 相关区域和血红素相关区域。我们将研究血红素缺失以及 CBS 的 AdoMet 和血红素结合区域中选择性突变的生化后果，以确定三种辅助因子如何在酶的生理功能中相互作用。该项目是 Kraus 实验室（在同型半胱氨酸代谢的生理学和分子遗传学方面拥有专业知识）和 Burstyn 实验室（在血红素蛋白结构和功能方面拥有专业知识）之间的综合合作成果。为了实现我们的目标，我们将结合生理学、生化和生物物理方法来了解血红素在 CBS 中的作用。继续该项目的具体目标是：1) 检验血红素对于 AdoMet 调节和人类 CBS 蛋白功能稳定性至关重要的假设，2) 检验 AdoMet 反应受损与血红素异常行为相关的假设或 PLP，以及 3) 检验 CBS 血红素稳定活性位点 PLP 以及这种相互作用的破坏会损害 CBS 功能的假设。叙述有些人的基因存在错误一种名为 CBS 的重要蛋白质，其作用是从血液中去除同型半胱氨酸分子。这些人很可能出现血栓或中风，因为他们的 CBS 蛋白不能正常工作，而且同型半胱氨酸水平过高。该项目着眼于 CBS 蛋白中的错误，并尝试从这些错误中了解该蛋白的正常工作原理。