A variety of approach toward creating artificial metalloenzymes (ArMs) have recently emerged all over the world. ArMs are defined as highly regio- and/or enantioselective catalysts consisting of a protein matrix and a synthetic metal complex. Thus, ArMs can harness excellent reactivity derived from the metal complexes as well as enzymatic properties such as exquisite chemical micro-environment to accelerate even difficult and desirable chemical reactions.
We have developed ArMs by repurposing a cupin-type protein (TM1459) obtained from hyperthermophile, Thermotoga Maritima, the metal center of which are composed of well-defined amino acid residues. This metal binding site consists of 4-histidine residues (4-his tetrad) in a same geometry to that of the tris(2-pyridylmethyl)amine (TPA) ligand system. By using this protein as a metal-ligands, we have recently developed the artificial non-heme metalloenzyme with high stereoselectivity. We mutated these four histidine residues to alanine to produce a variety of coordination mode at the metal binding site for asymmetric reactions. Based on this strategy, we developed artificial metalloenzymes that catalyzes dihydroxylation, Michael addition, cyclopropanation, and inverse electron-demand hetero Diels-Alder reaction. In this presentation, we report recent results.