CARNITINE METABOLISM & RELEVANT HYDROXYLATIONS

肉碱代谢

• 批准号: 3226900
• 负责人: SASHA ENGLARD
• 金额: $ 26.66万
• 依托单位: ALBERT EINSTEIN COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 1978
• 资助国家: 美国
• 起止时间: 1978-04-01 至 1989-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3226900
• 关键词: Neurospora; Pseudomonas; analytical method; carnitine; catalase; enzyme induction /repression; enzyme structure; hemoprotein; hydroxylation; lipid metabolism; liver; lysine; metalloproteins; nutrition related tag; radiotracer; stereochemistry; vitamin biosynthesis

Carnitine is important in normal oxidation of fatty acids for energy. It is provided to mammals from animal protein foods and by de novo synthesis from lysine incorporated into tissue proteins that then is trimethylated. Such proteins are degraded so that tissues including liver, heart, kidney and especially skeletal muscle have free intracellular trimethyllysine that can be converted to carnitine in several enzymatic steps including two hydroxylations catalyzed by Alpha-ketoglutarate-dependent, ascorbate-requiring dioxygenases. The liver is the major organ for final synthesis of carnitine by hydroxylation of Gamma-butyrobetaine. Carnitine levels appear to increase in various ketotic and incipient ketotic states such as diabetes and starvation; this remains to be firmly established, especially whether the increase is due to increased synthesis. We are engaged in a long-term study of metabolism and functions of carnitine, including synthesis, regulation of its synthesis and use, and degradation by intestinal bacteria. Here we propose, by studies using isolated perfused livers of rats, to learn whether increased synthesis occurs when the donor animals have been made diabetic by alloxan or streptozotocin, have been starved, or have received glucagon or the hypolipidemic drug, clofibrate. We then shall study capacities of homogenates of various tissues of normal and above animals to convert trimethyllysine and subsequent intermediates to Gamma-butyrobetaine or, in the liver to carnitine, we shall infer inter-organ dependencies in carnitine biosynthesis. Using isolated perfused livers from ascorbate-deficient guinea pigs, we shall determine whether ascorbate deficiency affects one or both hydroxylases in synthesis of carnitine. Then we shall study the mechanism of hydroxylation of Gamma-butyrobetaine to carnitine at a molecular level, selecting from amoung four proposed mechanisms. For that purpose we shall determine whether the reaction is stereospecific or steroeselective, and measure kinetic isotope effects. Finally, we outline methods to establish pathways of degradation of carnitine to trimethylamine and other products to be identified; the bacteria Ps. putida and Ac. calcoaceticus will be studied. We shall purify the enzyme(s) involved and study mechanisms of action. These organisms may serve as models for further study of truley enteric organisms of the human that could metabolize dietary carnitine and Gamma-butyrobetaine.

肉毒碱是重要的正常氧化脂肪酸的能量。 它 从动物蛋白质食物和通过从头合成提供给哺乳动物 从赖氨酸结合到组织蛋白中，然后三甲基化。 这些蛋白质被降解， 尤其是骨骼肌具有游离的细胞内三甲基赖氨酸， 可以在几个酶促步骤中转化为肉毒碱， 由α-酮戊二酸依赖性催化的羟基化， 需要抗坏血酸的双加氧酶。 肝脏是最终的主要器官 γ-丁酰基甜菜碱羟基化合成肉毒碱 肉碱 在各种酮化和初始酮化状态下， 如糖尿病和饥饿;这一点仍有待确定， 尤其是这种增加是否是由于合成增加。 我们 长期从事肉毒碱的代谢和功能研究， 包括合成、合成和使用的调节以及降解 被肠道细菌感染 在这里，我们建议，通过研究使用孤立的 灌注大鼠的肝脏，以了解是否增加合成发生时， 供体动物已通过四氧嘧啶或链脲佐菌素制成糖尿病， 已经挨饿，或者已经接受胰高血糖素或降血脂药物， 氯贝特 然后，我们将研究各种匀浆的能力， 正常和以上动物的组织转化三甲基赖氨酸， 随后的中间体γ-丁酰甜菜碱，或在肝脏中， 肉毒碱，我们将推断肉毒碱的器官间依赖性 生物合成 使用离体灌注的肝脏， 豚鼠，我们将确定是否抗坏血酸缺乏影响一个或 这两种羟化酶都参与合成肉毒碱。 然后我们将研究 γ-丁酰甜菜碱羟基化合成肉毒碱的机理 分子水平，从ammonium四个建议的机制。 为此 目的我们将确定该反应是否是立体特异性的或 立体选择性，并测量动力学同位素效应。 最后，我们概述 建立肉毒碱降解为三甲胺的途径的方法 和其他待鉴定的产物;细菌Ps. putida和Ac. 将研究醋酸钙。 我们将纯化所涉及的酶， 研究行动机制。 这些生物体可以作为 进一步研究人类肠道微生物， 代谢膳食肉毒碱和γ-丁酰甜菜碱。