Expanding Biocatalysis

Non-Natural Activities

Directed evolution is revolutionizing how we make molecules. But we do not want to be limited by the finite repertoire of natural enzymes – we want to create enzymes to cover a larger chemical universe. To address this challenge, we are repurposing existing proteins for new chemistries. Driven by mechanistic insights, we identify reactive intermediates (e.g. metal-carbenoid, -nitrenoid, -oxo, etc.) that can be harnessed for new-to-nature transformations. Directed evolution can tune these new enzymes and open up whole new routes to constructing C–X bonds with unmatched activity and selectivity.

 

Heme Protein Diversity

Nature’s diverse heme-binding proteins carry out many biochemical tasks critical to life: globins store oxygen in the blood, cytochromes c transport electrons in photosynthesis and central metabolism, and cytochromes P450 help metabolize xenobiotic compounds and participate in plant-animal warfare. Although nature selected these proteins to perform these native functions, many also have low levels of promiscuous activities for other reactions that may not be used in the natural setting. We use this diversity of heme proteins and their non-natural promiscuous, functions as the basis for evolving new enzymes in the laboratory. We create new enzymes that catalyze non-biological reactions with high efficiencies and selectivities.

For example, we used the truncated hemoglobin from Bacillus subtilis to catalyze cyclopropanation of an olefin for pharmaceutical production, cytochrome c from Rhodothermus marinus to form carbon-silicon bonds, and cytochrome P450 from Bacillus megaterium to catalyze intermolecular C-H amination.
Papers to start with

“Highly Stereoselective Biocatalytic Synthesis of Key Cyclopropane Intermediate to Ticagrelor”   K. E. Hernandez, H. Renata, R. D. Lewis, S. B. J. Kan, C. Zhang, J. Forte, D. Rozzell, J. A. McIntosh, F. H. Arnold. ACS Catalysis 6, 7810-7813 (2016). doi: 10.1021/acscatal.6b02550.

“Directed Evolution of Cytochrome c for Carbon-Silicon Bond Formation: Bringing Silicon to Life”  S.B. J. Kan, R. D. Lewis, K. Chen, F. H. Arnold. Science 354, 1048-1051 (2016). doi: 10.1126/science.aah6219.

“Enantioselective, Intermolecular Benzylic C-H Amination Catalysed by an Engineered Iron-Haem Enzyme”  C. K. Prier, R. K. Zhang, A. R. Buller, S. Brinkmann-Chen, F. H. Arnold. Nature Chemistry 9, 629-634 (2017). doi:10.1038/NCHEM.2783.