Defining the structure of ferryl heme

金属催化的氧活化是生物学的基石。它通常是使用金属离子实现的，通常是铜或铁。在铁的情况下，既有非含血红素的酶，也有含血红素的酶，它们能激活氧气。这个应用程序侧重于后者。激活的机制涉及形成标志性的化合物I和化合物II中间体，它们被用于一组不同的催化血红素酶，包括所有的细胞色素P450(参与药物代谢)、一氧化氮合酶(参与细胞信号传递)和末端氧化酶(参与呼吸)，以及血红素双加氧酶(参与NAD的形成)和血红素过氧化物酶(参与过氧化氢解毒)。化合物I和II是许多过程中的关键中间体，因此定义它们的结构和了解它们的反应活性，特别是它们的质子化状态，一直是几十年来该领域的一个关键问题。我们打算使用中子结晶学来决定性地推动这一领域的发展。我们打算获得化合物II的中子晶体结构，我们提出了三种策略来实现这一目标。这将确定化合物II中间体中所有质子的位置，并使我们能够在整个血红素酶家族中进行机械比较。这些都是雄心勃勃、技术困难且耗时的实验。但可能的收获是非常高的，因为我们最终有机会解决整个社会多年来一直未能解决的问题。

Metal-catalysed activation of oxygen is a cornerstone of biology. It is usually achieved using metal ions, typically either copper or iron. In the case of iron, there are both non-heme-containing and heme-containing enzymes which activate oxygen. This application focuses on the latter. The mechanism of activation involves formation of the iconic Compound I and Compound II intermediates, which are used across a diverse group of catalytic heme enzymes that include all the cytochrome P450s (involved in drug metabolism), the nitric oxide synthases (involved in cell signalling), and the terminal oxidases (involved in respiration), plus the heme dioxygenases (involved in formation of NAD) and heme peroxidases (involved in peroxide detoxification). Compounds I and II are such crucial intermediates in so many processes that defining their structure and understanding their reactivity, and in particular their protonation states, has been a key question in the field over several decades. We intend to use neutron crystallography to decisively advance the field in this area. We intend to obtain neutron crystal structures of Compound II, and we propose three strategies to deliver this. This will identify the locations of all the protons in the Compound II intermediate and will allow us to make mechanistic comparisons across the family of heme enzymes. These are ambitious, technically difficult and time-consuming experiments. But the likely gains are very high, because we have chance to finally resolve questions that have eluded the whole community for many years.