CARNITINE METABOLISM & RELEVANT HYDROXYLATIONS

肉碱在脂肪酸正常氧化为能量的过程中很重要。它 从动物蛋白食物和从头合成中提供给哺乳动物 从结合到组织蛋白质中的赖氨酸，然后被三甲基化。 这样的蛋白质被降解，从而使包括肝脏、心脏、肾脏在内的组织 尤其是骨骼肌细胞内含有游离的三甲基赖氨酸 可以通过几个酶步骤转化为肉碱，包括两个步骤 依赖于α-酮戊二酸催化的羟基化反应， 需要抗坏血酸的双加氧酶。肝脏是期末考试的主要器官 γ-丁基甜菜碱羟基化合成肉碱。肉碱 在各种酮症和初发酮症状态中，水平似乎都会增加 例如糖尿病和饥饿；这一点仍有待牢固确立， 尤其是这种增加是否由于合成增加所致。我们是 从事肉碱代谢和功能的长期研究， 包括合成、对其合成和使用的调节以及降解 被肠道细菌感染。在这里，我们提出，通过使用孤立的研究 灌流大鼠的肝脏，以了解当 供体动物因四氧嘧啶或链脲佐菌素而患上糖尿病， 曾挨饿，或接受过胰高血糖素或降血脂药物， 氯贝特。然后我们将研究各种不同匀浆的容量 正常及以上动物的组织转化三甲基赖氨酸和 随后的中间体为伽玛-丁甜菜碱，或，在肝脏中 肉碱，我们将推断肉碱的器官间依赖性 生物合成。使用抗坏血酸缺乏的隔离灌流肝脏 对于豚鼠，我们将确定抗坏血酸缺乏是否影响一个或多个 肉碱合成中的两种羟基酶。然后我们将研究 γ-丁基甜菜碱羟化为肉碱的反应机理 分子水平，从提出的四种机制中进行选择。为此， 目的我们将确定该反应是立体专一性的还是 立体选择性，并测量动力学同位素效应。最后，我们概述了 方法建立肉碱降解为三甲胺的途径 和其他有待鉴定的产品；细菌Ps。恶臭和恶臭。 将对醋酸钙进行研究。我们将提纯所涉及的酶(S)和 研究其作用机制。这些生物体可以作为 对人的特鲁利肠道微生物的进一步研究 代谢饮食中的肉碱和伽马-丁甜菜碱。

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.