Radical Biocatalysis: Using Non-Natural Single Electron Transfer Mechanisms to Access New Enzymatic Functions

Exploiting non-natural reaction mechanisms within native enzymes is an emerging strategy for expanding the synthetic capabilities of biocatalysts. When coupled with modern protein engineering techniques, this approach holds great promise for biocatalysis to address long-standing selectivity and reactivity challenges in chemical synthesis. Controlling the stereochemical outcome of reactions involving radical intermediates, for instance, could benefit from biocatalytic solutions because these reactions are often difficult to control by using existing small molecule catalysts. General strategies for catalyzing non-natural radical reactions within enzyme active sites are, however, undeveloped. In this account, we highlight three distinct strategies developed in our group that exploit non-natural single electron transfer mechanisms to unveil previously unknown radical biocatalytic functions. These strategies allow common oxidoreductases to be used to address the enduring synthetic challenge of asymmetric hydrogen atom transfer. 1 Introduction 2 Photoinduced Electron Transfer from NADPH 3 Ground State Electron Transfer from Flavin Hydroquinone 4 Enzymatic Redox Activation in NADPH-Dependent Oxidoreductases 5 Conclusion.