Artificial β-propeller protein-based hydrolases.

We developed an artificial hydrolase based on the symmetrical Pizza6 beta-propeller protein for the metal-free hydrolysis of 4-nitrophenyl acetate and butyrate. Through site-specific mutagenesis and crystallisation studies, the catalytic mechanism was investigated and found to be dependent on a threonine-histidine dyad. The mutant with additional histidine residues generated the highest k(cat) values, forming a His-His-Thr triad and matched previously reported metalloenzymes. The highly symmetrical beta-propeller artificial enzymes and their protein-metal complexes have potential to be utilised in bioinorganic and supramolecular chemistry, as well as being developed further into 2D/3D catalytic materials.