Artificial metalloenzymes (ArMs) result from combining an organometallic catalyst in a protein scaffold. The resulting hybrid catalyst display advantageous features from both homogeneous catalyst (e.g. broad reaction repertoire) and enzymes (e.g. evolvable catalytic performance via genetic mutations). Within the DrEAM ERC project, we set out to assemble, evolve and exploit ArMs in a cellular environment, thus enabling the use of bacterial cells as molecular factories (or as "test-tubes") for the synthesis of high-added value chemicals.
Today, chemical transformations are typically carried out in pure organic solvents and in a stepwise fashion. In stark contrast biochemical transformations proceed in a complex cellular environment and to not require the isolation of the chemical intermediates along the multistep reaction sequence. The latter strategy presents multiple advantages, both from an economic and environmental perspective: “using a cell as test-tube or a molecular factory”.
During the DrEAM ERC project, we demonstrated ArMs can indeed be assembled, and evolved in a cellular environment. In addition, they can be combined with natural enzyme leading to efficient enzyme cascades, whereby a substrate is converted via multiple (artificial) enzymes into a product. These findings demonstrate that cells can indeed be used as test-tube whereby both natural enzymes and ArMs work in concert in a complex environment.
To achieve these ambitious goals, two protein scaffolds were evaluated: human carbonic anhydrase II and streptavidin. The following ArMs-catalyzed new-to-nature reactions were implemented and optimized in a cellular environment: transfer hydrogenation, allylic substitution, cyclopropanation, olefin metathesis and hydroamination.
In summary, the field of ArMs has enormously progressed, thanks to the DrEAM ERC grant. Gratifyingly, our work is widely acclaimed as has inspired many groups to follow our footsteps. Currently, more than fourty groups worldwide are active in the field.
