Characterisation and Inhibition of Carnitine Biosynthesis Oxygenases

脂肪酸是人类和大多数其他生命形式的主要能量来源。为了代谢脂肪酸，它们必须被运输到称为线粒体的细胞内空间，在那里它们被氧气依赖的呼吸过程代谢，产生化学能，这对我们所做的一切都是必不可少的。然而，当我们摄入的脂肪酸超过我们的新陈代谢能力时，它们就会被储存起来，导致体重增加，最终导致肥胖和相关疾病。脂肪酸进入线粒体的过程需要它们与一种名为肉碱的分子结合，肉碱之所以被称为肉碱，是因为它在动物肌肉中存在于高水平，即肉类中。我们人类都制造肉碱，并从我们的饮食中获得。肉碱被广泛用作减肥补充剂，因为它促进脂肪代谢。人类产生肉碱的起点是蛋白质，这些蛋白质被降解，产生一种不寻常的氨基酸，称为三甲基赖氨酸或TML。TML通过一系列酶催化步骤转化为肉碱，其中两个步骤由加氧酶催化，即利用氧气进行催化的酶。米屈肼是一种临床使用的化合物，它至少能抑制其中一种加氧酶。米屈肼是在患者心脏病发作后服用，以抑制脂肪酸的生物合成。这是因为脂肪酸的生物合成会产生有害的活性氧化物质作为副产品，而这些物质在心脏病发作后被认为特别危险。我们最近在通过解算目标的晶体结构来了解米屈肼的工作原理方面取得了突破性进展。我们还发现，米屈肼不是一个简单的酶抑制剂，事实上，它是一种正在经历一种前所未有的反应的底物，涉及其分子结构的重排。这项工作也使我们处于异常有利的地位，可以了解米屈肼在人类细胞中的实际作用，并揭开我们和其他动物如何制造肉碱的分子细节。我们对探索肉碱生物合成和遗传学之间的联系特别感兴趣，因为当肉碱存在于DNA结合蛋白(称为组蛋白)中时，TML还参与调节细胞中哪些基因的打开和关闭。重要的是，我们有很好的证据表明，我们可以开发改进版本的米屈肼，我们将向对脂肪酸代谢感兴趣的广大研究人员提供这种药物。我们将研究肉碱生物合成加氧酶的结构和机制，并开发改进的抑制剂，作为肉碱生物合成加氧酶的生理作用的功能探针。在我们发现肉碱生物合成酶的不同寻常的化学成分的基础上，我们还将评估它们生产对制药行业有用的化学品的潜力。

Fatty acids are a major energy source for humans and most other life forms. In order for fatty acids to be metabolised they must be transported into intracellular compartments called mitochondria, where they are metabolised by the oxygen dependent process of respiration to generate chemical energy that is essential for absolutely everything we do. However, when we consume more fatty acids than we can metabolise they are stored, leading to weight gain and, ultimately, obesity and related diseases. The process of fatty acid transport into mitochondria requires their conjugation to a molecule called carnitine, so named because it is present at high levels in animal muscle, i.e. meat. We humans both make carnitine and obtain it from our diet. Carnitine is widely used as a dietery supplement because it promotes fat metabolism. The starting points for carnitine production in humans are proteins that are degraded to give an unusual amino acid called trimethyl-lysine or TML. TML is converted into carnitine by a series of enzyme-catalysed steps, two of which are catalysed by oxygenases, i.e. enzymes that use oxygen for catalysis. Mildronate, a clinically used compound, inhibits at least one of these oxygenases. Mildronate is given to patients after they have had a heart attack, in order to inhibit fatty acid biosynthesis. This is because fatty acid biosynthesis produces damaging reactive oxidising species as byproducts and these are thought to be particularly dangerous after heart attacks. We have recently made a breakthrough in work aimed at understanding how Mildronate works by solving crystal structures of its target. We have also found that Mildronate is not a simple enzyme inhibitor but is, in fact, a substrate undergoing an unprecedented reaction involving rearrangement of its molecular structure. This work has also placed us in an exceptionally good position to understand how Mildronate actually works in human cells and to unravel the molecular details of how we and other animals make carnitine. We are particularly interested in exploring links between carnitine biosynthesis and genetics because, when it is present in DNA binding proteins called histones, TML is also involved in regulating which genes are 'turned on and off' in cells. Importantly we have good evidence that we can develop improved versions of Mildronate, which we will make available to the large community of researchers interested in fatty acid metabolism. We will investigate the structure and mechanism of the oxygenases of carnitine biosynthesis and develop improved inhibitors that will be useful as functional probes for the physiological roles of the carnitine biosynthesis oxygenases. Building upon our discovery the unusual chemistry of the carnitine biosynthesis enzymes, we will also evaluate their potential for the production of chemicals that will be of use to the pharmaceutical industry.