The plasticity of redox cofactors: from metalloenzymes to redox-active DNA

Metal cofactors considerably widen the catalytic space of naturally occurring enzymes whose specific and enantioselective catalytic activity constitutes a blueprint for economically relevant chemical syntheses. To optimize natural enzymes and uncover novel reactivity, we need a detailed understanding of cofactor–protein interactions, which can be challenging to obtain in the case of enzymes with sophisticated cofactors. As a case study, we summarize recent research on the [FeFe]-hydrogenases, which interconvert protons, electrons and dihydrogen at a unique iron-based active site. We can now chemically synthesize the complex cofactor and incorporate it into an apo-protein to afford functional enzymes. By varying both the cofactor and the polypeptide components, we have obtained detailed knowledge on what is required for a metal cluster to process H2. In parallel, the design of artificial proteins and catalytically active nucleic acids are advancing rapidly. In this Perspective, we introduce these fields and outline how chemists and biologists can use this knowledge to develop novel tailored semisynthetic catalysts. The study of [FeFe]-hydrogenases exemplifies how one can manipulate even sophisticated metal clusters to afford insights into structure–function relationships of biological catalysts. This Perspective describes developments in designing artificial proteins and catalytically active nucleic acids towards minimalistic and robust semi-biological catalysts for chemical synthesis.