Functional assignments on human oxygenases

对于从细菌到人类的所有需氧生物来说，调节细胞的氧气输送都是一个问题。在哺乳动物中，肺、心脏和血液都致力于这一任务，而人类的疾病(如中风、心脏病发作和贫血)往往涉及低氧水平(缺氧)对器官的损害。由BBSRC支持的基础科学工作为细胞如何“感知”和应对缺氧提供了洞察力。这项工作帮助确定了一组催化将大气中的氧气结合到底物中的加氧酶(一种酶)，这种加氧酶催化氧原子添加到一种名为缺氧诱导因子(HIF)的蛋白质中，之所以被称为HIF，是因为它的水平在低氧浓度下会上升。HIF很重要，因为它存在于包括昆虫、蠕虫和人类在内的非常广泛的生物体中；它使一系列基因得以表达，这些基因有助于有机体克服缺氧的挑战。在人类中，这些基因能够对缺氧做出反应，包括那些参与血管和红细胞形成的基因。向HIF中添加氧气会阻止其表达与低氧反应有关的基因。当有足够的氧气时，加氧酶可以催化其加成到HIF上，但当氧气水平下降时，HIF不再被修饰，它可以自由地使参与缺氧反应的基因表达。我们希望这项工作的结果将导致涉及心血管系统的疾病的新疗法。通过用小分子药物抑制HIF加氧酶，应该可以提高人体对低氧浓度损伤的自然防御能力。然而，为了安全地完成这项工作而不引起副作用，需要更多地了解其他人类加氧酶，这些知识已经通过对人类基因组的分析而揭示出来。关于HIF系统的工作提出了关于加氧酶在控制其他途径甚至整个生物学中基因表达的作用程度的问题。这项提议试图通过研究人类加氧酶来解决这些问题，其中一些已知在生理水平的工作中具有生物医学重要性，但很少或根本没有关于其在生化水平上的实际底物和作用的数据。例如，与来自微生物的细胞相比，使用人类细胞存在技术问题。然而，我们选择与人类酶合作，部分是因为全球在基因组测序和其他大规模项目中研究人类细胞中存在的蛋白质的努力提供了一个资源，我们可以利用它来帮助分配加氧酶的生化角色，部分原因是我们希望这项工作将有助于在更好地了解人类新陈代谢的基础上开发新的疗法。

Regulating oxygen delivery to cells is a problem for all aerobic organisms ranging from bacteria to humans. In mammals, the lungs, heart and blood are all devoted to this task, and human diseases (such as strokes, heart attacks and anaemia) often involve damage to organs by low oxygen levels (hypoxia). Basic science work supported by the BBSRC has provided insights into how cells 'sense' and respond to hypoxia. The work has helped to identify a set of 'oxygenases' (a type of enzyme that catalyses the incorporation of atmospheric oxygen into their substrates) that catalyse the addition of oxygen atoms to a protein called hypoxia inducible factor (HIF), so called because its level is raised under low oxygen concentrations. HIF is important as it occurs in a very wide range of organisms including insects, worms and humans; it enables the expression of a range of genes that work to help the organism overcome the challenge of hypoxia. In humans these genes enable a response to hypoxia and include those involved in blood vessel and red blood cell formation. Addition of oxygen to HIF stops its ability to enable the expression of the genes involved in the hypoxic response. When there is sufficient oxygen the oxygenases can catalyse its addition to HIF, but when oxygen levels fall HIF is no longer modified and it is free to enable expression of the genes involved in the hypoxic response. We hope that the results of this work will result in new treatments for diseases involving the cardiovascular system. By inhibiting the HIF oxygenases with small molecule drugs, it should be possible to improve the body's natural defence against damage from low oxygen concentrations. However to do this safely without causing side effects will require more knowledge of other human oxygenases, that have been revealed by analysis of the human genome. The work on the HIF system has raised questions as to the extent of the role of oxygenases in controlling the expression of genes in other pathways and indeed biology as a whole. This proposal seeks to go some way towards addressing these questions by studying human oxygenases, some of which are known to be biomedicinally important from work at the physiological level but for which there is little or no data in terms of their actual substrates and roles at a biochemical level. There are technical problems in working with human cells compared to, for example, those from microorganisms. However, we have chosen to work with human enzymes, in part, because the worldwide efforts in genome sequencing and other large scale projects studying the proteins present in human cells have provided a resource we can utilise to help assign biochemical roles for the oxygenases, and, in part, because we hope that the work will be useful in the development of new therapies based on a better understanding of human metabolism.