Redox-reversible artificial metalloenzymes

作为天然的生物催化剂，酶经过数十亿年或数年的进化而变得高效和有选择性。由于它们的可持续性和环境兼容性，它们在生物转化和化学合成中的应用都很有吸引力。然而，对于许多应用，合适的自然产生的酶是不可用的。另一方面，量身定制的人造金属酶可以将蛋白质的选择性和生物相容性与合成催化剂的反应性和反应范围结合起来，从而有可能扩大生物催化剂的应用范围，例如通过使新的自然转化变得容易。人工金属酶尚未进入普遍使用，主要是因为蛋白质和催化剂的生产具有挑战性和昂贵，当人工酶不再需要或不再活跃时，其有价值的成分不容易回收。受细菌获取必需铁的方式的启发，我们开发了一种新的铁基锚定单元，它将合成催化剂连接到蛋白质上，产生人造酶，但在铁中心的化学还原时，锚定单元断开并触发人造酶的分解。因此，蛋白质和合成催化剂都可以回收和再循环。在这个项目中，我们将探索这些可回收人造酶的更广泛范围，并将蛋白质支架固定在固体载体上，使其能够整合到流动系统中。这样，就有可能移除和更换失去活性的催化剂。随后用不同的催化剂进行替换将特别令人感兴趣，因为这不仅可以使蛋白质循环使用，而且可以很容易地从一种催化反应切换到另一种催化反应。将这种“捕捉和释放”方法应用于固定化人造金属酶设计，将为它们的制备提供一个灵活的工具箱，允许催化剂、蛋白质支架和固体载体混合、匹配和回收，供我们和其他人在批处理和连续流动中使用、适应和进一步探索。

As natural biocatalysts, enzymes have evolved over billions or years to be highly efficient and selective. Their application in both bioconversions and chemical syntheses is attractive because of their sustainability and environmental compatibility. However, for many applications, suitable naturally occurring enzymes are not available. Tailor-made artificial metalloenzymes, on the other hand, can combine the selectivity and biocompatibility of proteins with the reactivity and the reaction scope of synthetic catalysts and thus have the potential to expand the range of applications in which biocatalysts can be used, for example by making new-to-nature transformations accessible. Artificial metalloenzymes have not yet progressed into general use, mainly because the proteins and the catalysts are challenging and expensive to produce and, when the artificial enzyme is no longer required or active, its valuable components cannot easily be recycled.Inspired by the way bacteria acquire essential iron, we have developed a new iron-based anchor unit that connects synthetic catalysts to proteins, creating artificial enzymes, but on chemical reduction of the iron centre, the anchor unit disconnects and triggers the disassembly of the artificial enzymes. Hence both the protein and the synthetic catalyst can be recovered and recycled.In this project, we will explore the wider scope of these recyclable artificial enzymes and immobilise the protein scaffolds on solid supports to enable their integration into flow systems. In this way, the removal and replacement of catalysts that have lost activity becomes possible. Subsequent replacements with different catalysts would be of particular interest since this would not only allow the protein to be recycled but also enabling an easy switch from one catalysed reaction to another. The application of this 'catch-and-release' approach to immobilised artificial metalloenzyme design will provide a flexible toolbox for their preparation that allows catalysts, protein scaffolds and solid supports to be mixed, matched and recycled, for us and others to use, adapt and explore further, both in batch processes and in continuous flow.