Synthetic cascades are enabled by combining biocatalysts with artificial metalloenzymes


Enzymatic catalysis and homogeneous catalysis offer complementary means to address synthetic challenges, both in chemistry and in biology. Despite its attractiveness, the implementation of concurrent cascade reactions that combine an organometallic catalyst with an enzyme has proven challenging because of the mutual inactivation of both catalysts. To address this, we show that incorporation of a d6-piano stool complex within a host protein affords an artificial transfer hydrogenase (ATHase) that is fully compatible with and complementary to natural enzymes, thus enabling efficient concurrent tandem catalysis. To illustrate the generality of the approach, the ATHase was combined with various NADH-, FAD- and haem-dependent enzymes, resulting in orthogonal redox cascades. Up to three enzymes were integrated in the cascade and combined with the ATHase with a view to achieving (i) a double stereoselective amine deracemization, (ii) a horseradish peroxidase-coupled readout of the transfer hydrogenase activity towards its genetic optimization, (iii) the formation of L-pipecolic acid from L-lysine and (iv) regeneration of NADH to promote a monooxygenase-catalysed oxyfunctionalization reaction.

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Figure 1: Reaction cascades resulting from combining an ATHase with a biocatalyst.
Figure 2: Overview of reaction cascades scrutinized in this study.
Figure 3: Enzyme cascade for the double stereoselective deracemization of amines.
Figure 4: Colorimetric assay for the determination of ATHase activity in an enzyme cascade.
Figure 5: Expanding the concept of orthogonal redox cascades to include other enzymes.


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This work was supported by the Marie Curie Initial Training Network (Biotrains FP7-ITN-238531). T.R.W. acknowledges financial support from the SNF (Schweizerische Nationalfonds, grant no. 200020_126366) and the National Centre of Competence in Research Nanosciences. N.J.T. acknowledges the Royal Society for a Wolfson Research Merit Award. F.H. thanks A. Schmid (Dortmund University of Technology) for the kind provision of HbpA. The authors also thank M. Corbett, S. Willies and K. Malone for helpful advice and materials, R. Pfalzberger for help with the graphic material, and Umicore for a precious metal loan.

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V.K., F.H., N.T. and T.W. conceived the catalytic cascades. V.K., F.H., N.T. and T.W. supervised the project. V.K., Y.W., M.D., D.G., E.C. and T.Q. performed the experiments. V.K., Y.W., M.D., D.G., E.C., T.Q., F.H., N.T. and T.W. analysed the data. V.K., F.H., N.T. and T.W. co-wrote the paper. V.K., Y.W., M.D., D.G. and L.K. contributed materials. D.H. analysed the conversion of 13C-labelled lysine by 2D NMR.

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Correspondence to F. Hollmann or N. J. Turner or T. R. Ward.

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The authors declare no competing financial interests.

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Köhler, V., Wilson, Y., Dürrenberger, M. et al. Synthetic cascades are enabled by combining biocatalysts with artificial metalloenzymes. Nature Chem 5, 93–99 (2013).

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