Solar‐Powered Whole‐Cell P450 Catalytic Platform for C‐Hydroxylation Reactions

Abstract

Photobiocatalysis is a green platform for driving redox enzymatic reactions using solar energy, not needing high‐cost cofactors and redox partners. Here, a visible light‐driven whole‐cell platform for human cytochrome P450 (CYP) photobiocatalysis was developed using natural flavins as a photosensitizer. Photoexcited flavins mediate NADPH/reductase‐free, light‐driven biocatalysis by human CYP2E1 both in vitro and in the whole‐cell systems. In vitro tests demonstrated that the photobiocatalytic activity of CYP2E1 is dependent on the substrate type, the presence of catalase, and the acid type used as a sacificial electron donor. A protective effect of catalase was found against the inactivation of CYP2E1 heme by H2O2 and the direct transfer of photo‐induced electrons to the heme iron not by peroxide shunt. Furthermore, the P450 photobiocatalysis in whole cells containing human CYPs 1A1, 1A2, 1B1, and 3A4 demonstrated the general applicability of the solar‐powered, flavin‐mediated P450 photobiocatalytic system.

Unbiased Photoelectrode Interfaces for Solar Coupling of Lignin Oxidation with Biocatalytic C═C Bond Hydrogenation

“…Overall, this study demonstrates that α-Fe 2 O 3 extracts electrons from lignin wastes for driving enantioselective hydrogenation reactions with excellent performances. We envision that the PEC regeneration of mNADHs can be further applied to activate various redox enzymes , (e.g., cytochrome P450, enoate reductase, monooxygenase, d -lactate dehydrogenase, malic enzyme, and malate dehydrogenase) for solar-to-chemical conversion. Future challenges for attaining higher photobiocatalytic efficiencies would be (i) photoanode’s doping or morphological/dimensional change to increase hole concentrations at the semiconductor–electrolyte interface, (ii) investigation of α-Fe 2 O 3 ’s active sites for lignin oxidation and augmentation of the active sites to boost the lignin oxidation reaction, (iii) functionalization of the cathode with graphitic carbon materials to accelerate charge transfer to M1 , and (iv) modification of mediator’s redox potential to enhance (m)­NADH regeneration performance.…”

Light-driven biocatalytic oxidation

“…Photobiocatalytic oxidation is an emerging synthetic route but still in infancy. For example, only a few cases of light-driven monooxygenase catalysis have been reported, 12,13,29,31,36 and their catalytic activities are quite low (TTN < 1000). For operation of H 2 O 2 -accepting enzymes, light-driven in situ H 2 O 2 generation is advantageous because it uses a clean light energy source and does not need any cofactors and additional enzymes.…”

“…12 For human CYP2E1, in contrast, the avin/EDTA/light system works only via direct transfer of light-induced electrons to the P450 heme iron, not by the H 2 O 2 -mediated peroxide shunt. 13 Indirect transfer of photoinduced electrons to monooxygenases has been extensively accomplished through photochemical reduction of biological cofactors [e.g., NAD(P)H, FADH 2 ]. Here, the redox mediators function as a freely diffusing, remote communicator between a photocatalyst and a monooxygenase.…”

“…In addition to the photosensitizing dyes ( e.g. , flavin, 12,13 EY 31 ), ruthenium (Ru) 36 complexes have been used as a photocatalyst to reduce P450 heme iron (Fig. 2b).…”

Artificial photosynthesis systems for solar energy conversion and storage: platforms and their realities

“…Recently, they fabricated a whole-cell APS containing human cytochrome P450 (CYP) using natural flavins as a photosensitizer to activate the biocatalyst directly. 109 However, H 2 O 2 and superoxide were derived unavoidably by the reduced FMN that could inhibit the CYP activity. CYP destruction might be overcome by introducing exogenetic catalase, which, however, would compromise the practicability of this APS.…”