Functional assignments on human oxygenases

从细菌到人类，对所有需氧生物来说，调节向细胞输送氧气都是一个难题。在哺乳动物中，肺、心脏和血液都致力于这项任务，而人类疾病（如中风、心脏病发作和贫血）通常涉及低氧水平（缺氧）对器官的损害。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见。这项工作有助于确定一组“加氧酶”（一种催化大气氧气进入其底物的酶），这些酶催化氧原子添加到一种称为缺氧诱导因子（HIF）的蛋白质中，这样称呼是因为它的水平在低氧浓度下会升高。HIF很重要，因为它发生在非常广泛的生物体中，包括昆虫、蠕虫和人类；它使一系列基因的表达能够帮助生物体克服缺氧的挑战。在人类中，这些基因能够对缺氧做出反应，包括那些与血管和红细胞形成有关的基因。向HIF中添加氧气会阻止其表达参与缺氧反应的基因的能力。当有足够的氧气时，加氧酶可以催化其加入HIF，但当氧气水平下降时，HIF不再被修饰，它可以自由地表达参与缺氧反应的基因。我们希望这项工作的结果将导致涉及心血管系统疾病的新治疗方法。通过用小分子药物抑制HIF加氧酶，应该有可能提高人体对低氧浓度损伤的天然防御能力。然而，要安全地做到这一点而不产生副作用，将需要对人类基因组分析所揭示的其他人类加氧酶有更多的了解。对HIF系统的研究提出了一些问题，如加氧酶在控制其他途径和整个生物学中基因表达方面的作用程度。本提案试图通过研究人体加氧酶来解决这些问题，其中一些已知在生理水平上具有重要的生物医学意义，但在其实际底物和生化水平上的作用方面几乎没有数据。与微生物细胞相比，使用人类细胞存在一些技术问题。然而，我们选择与人类酶一起工作，部分原因是全球范围内对人类细胞中蛋白质的基因组测序和其他大规模研究项目为我们提供了一种资源，我们可以利用它来帮助分配加氧酶的生化作用，部分原因是我们希望这项工作将有助于开发基于对人类代谢的更好理解的新疗法。

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.