Synergistic catalysis in an artificial enzyme by simultaneous action of two abiological catalytic sites

Abiological catalytic components can increase the synthetic potential of enzymes. This work reports an enzyme with two different abiological catalytic moieties-an organocatalytic unnatural amino acid and a metal complex-that act synergistically to achieve highly enantioselective Michael addition reactions. Artificial enzymes, which are hybrids of proteins with abiological catalytic groups, have emerged as a powerful approach towards the creation of enzymes for new-to-nature reactions. Typically, only a single abiological catalytic moiety is incorporated. Here we introduce a design of an artificial enzyme that comprises two different abiological catalytic moieties and show that these can act synergistically to achieve high activity and enantioselectivity (up to >99% e.e.) in the catalysed Michael addition reaction. The design is based on the lactococcal multidrug resistance regulator as the protein scaffold and combines a genetically encoded unnatural p-aminophenylalanine residue (which activates an enal through iminium ion formation) and a supramolecularly bound Lewis acidic Cu(ii) complex (which activates the Michael donor by enolization and delivers it to one preferred prochiral face of the activated enal). This study demonstrates that synergistic combination of abiological catalytic groups is a robust way to achieve catalysis that is normally outside of the realm of artificial enzymes.