Whole-cell-catalyzed hydrogenation/deuteration of aryl halides with a genetically repurposed photodehalogenase

The bigger pictureBiocatalysis has become a vital tool for sustainable organic synthesis. However, a contradiction exists between the demand for diverse unnatural chemical synthesis from mankind and the enzyme repertoire defined by nature. As such, the innovation of artificial enzymes with functions beyond those found in nature is highly desirable for advancing biocatalysis toward sustainable organic synthesis. Herein, we show that a genetically repurposed, metal cofactor-free photodehalogenase is capable of performing hydrogenation/deuteration of aryl halides and can be operated in a whole-cell catalysis fashion. This study highlights the potential of chemically driven, man-made photosynthetic machinery for advancing green chemical manufacturing.Highlights•An artificial photoenzyme encoding a synthetic photocatalyst•Photobiocatalytic dehalogenation with broad abiological aryl halides•Unprecedented photobiocatalytic site-selective deuteration•Whole-cell photoredox catalysis via a non-natural mechanismSummaryArtificial enzymes with new-to-nature reactivity are highly desirable to expand the repertoire of biocatalysis for sustainable synthesis. To this end, artificial photoenzymes embedded with a prominent photoredox catalyst established in synthetic chemistry can harness light energy to trigger electron transfer transformations of abiological substrates. Herein, we demonstrate that a benzophenone photocatalyst encoded in a yellow fluorescent protein named reductive photodehalogenase (RPDase) can proficiently mediate the biocatalytic hydrodehalogenation and deuterodehalogenation of aryl halides. Unlike natural metal-cofactor-dependent dehalogenases evolved for the bioremediation of specific substrates, this metal-free photoenzyme operates in combination with formate via an entirely unnatural catalytic mechanism and exhibits marked substrate generality. Taking advantage of the biorthogonality of RPDase and the genetic code expansion method, we further demonstrated the first whole-cell photobiocatalysis using recombinant Escherichia coli cells that express RPDase. Our results show that artificial enzymes bearing a synthetic organophotocatalyst is promising to generate a non-natural metabolism for valuable abiological reactions.Graphical abstract