Photocatalytic activity of hybrid P450 Enzymes

Abstract

The Cytochromes P450 are heme-thiolate enzymes that carry out selective oxyfunctionalization of a wide range of substrates using molecular dioxygen and two reducing equivalents provided by redox partner enzymes. Alternative approaches to activate P450 enzymes have received recent attention in an attempt to circumvent the use of redox partners and cofactors. In particular, the use of light-harvesting units has proven useful in triggering P450 activity upon visible light-excitation. Our laboratory has taken advantage of the inorganic Ru(II)-diimine photosensitizers and their unique excited properties to harness P450 synthetic potential. Their covalent attachment to non-native single cysteine residues has enabled rapid electron injection into the heme domain of several P450 enzymes leading to high photocatalytic activity and coupling efficiency. Recently, we also developed a bimolecular system to activate P450 with peroxygenase activity. The crystal structure of the most efficient hybrid enzyme reveals that the photosensitizer is ideally positioned to deliver electrons to the heme active site utilizing the natural electron transfer pathway. A combination of rational and directed evolution approaches are currently employed to optimize the biocatalyst photocatalytic activity and expand the scope of the light-driven P450 activity. In addition, the tunability and derivatization of the inorganic complexes have promoted the formation of dimeric structures and heterogeneous biocatalysts and provided insights into the rate-limiting steps in the light-driven hybrid P450 enzyme.