Fujieda, N.; Itoh, S.

Chem. - Asian J. 2012, 7, 1203-1207, 10.1002/asia.201101014

Teaching metalloenzymes new tricks: An artificial type III dicopper oxidase has been developed using a hydrolytic enzyme, metallo‐β‐lactamase, as a metal‐binding platform. The triple mutant D88G/S185H/P224G redesigned by computer‐assisted structural analysis showed spectroscopic features similar to those of type III copper proteins and exhibited a high catalytic activity in the oxidation of catechols under aerobic conditions.

Liu, J.

Chem. Soc. Rev. 2012, 41, 7890, 10.1039/c2cs35207a

Enzymes are nanometer-sized molecules with three-dimensional structures created by the folding and self-assembly of polymeric chain-like components through supramolecular interactions. They are capable of performing catalytic functions usually accompanied by a variety of conformational states. The conformational diversities and complexities of natural enzymes exerted in catalysis seriously restrict the detailed understanding of enzymatic mechanisms in molecular terms. A supramolecular viewpoint is undoubtedly helpful in understanding the principle of enzyme catalysis. The emergence of supramolecular artificial enzymes therefore provides an alternative way to approach the structural complexity and thus to unravel the mystery of enzyme catalysis. This critical review covers the recent development of artificial enzymes designed based on supramolecular scaffolds ranging from the synthetic macrocycles to self-assembled nanometer-sized objects. Such findings are anticipated to facilitate the design of supramolecular artificial enzymes as well as their potential uses in important fields, such as manufacturing and food industries, environmental biosensors, pharmaceutics and so on.

Fujieda, N.; Itoh, S.

J. Am. Chem. Soc. 2017, 139, 5149-5155, 10.1021/jacs.7b00675

Thermally stable TM1459 cupin superfamily protein from Thermotoga maritima was repurposed as an osmium (Os) peroxygenase by metal-substitution strategy employing the metal-binding promiscuity. This novel artificial metalloenzyme bears a datively bound Os ion supported by the 4-histidine motif. The well-defined Os center is responsible for not only the catalytic activity but also the thermodynamic stability of the protein folding, leading to the robust biocatalyst (Tm ≈ 120 °C). The spectroscopic analysis and atomic resolution X-ray crystal structures of Os-bound TM1459 revealed two types of donor sets to Os center with octahedral coordination geometry. One includes trans-dioxide, OH, and mer-three histidine imidazoles (O3N3 donor set), whereas another one has four histidine imidazoles plus OH and water molecule in a cis position (O2N4 donor set). The Os-bound TM1459 having the latter donor set (O2N4 donor set) was evaluated as a peroxygenase, which was able to catalyze cis-dihydroxylation of several alkenes efficiently. With the low catalyst loading (0.01% mol), up to 9100 turnover number was achieved for the dihydroxylation of 2-methoxy-6-vinyl-naphthalene (50 mM) using an equivalent of H2O2 as oxidant at 70 °C for 12 h. When octene isomers were dihydroxylated in a preparative scale for 5 h (2% mol cat.), the terminal alkene octene isomers was converted to the corresponding diols in a higher yield as compared with the internal alkenes. The result indicates that the protein scaffold can control the regioselectivity by the steric hindrance. This protein scaffold enhances the efficiency of the reaction by suppressing disproportionation of H2O2 on Os reaction center. Moreover, upon a simple site-directed mutagenesis, the catalytic activity was enhanced by about 3-fold, indicating that Os-TM1459 is evolvable nascent osmium peroxygenase.

Fujieda, N.; Itoh, S.

Angew. Chem. 2020, 132, 7791-7794, 10.1002/ange.202000129

Cupin superfamily proteins (TM1459) work as a macromolecular ligand framework with a double-stranded β-barrel structure ligating to a Cu ion through histidine side chains. Variegating the first coordination sphere of TM1459 revealed that H52A and H54A/H58A mutants effectively catalyzed the diastereo- and enantioselective Michael addition reaction of nitroalkanes to an α,β-unsaturated ketone. Moreover, calculated substrate docking signified C106N and F104W single-point mutations, which inverted the diastereoselectivity of H52A and further improved the stereoselectivity of H54A/H58A, respectively.

Liu, J.

Curr. Opin. Struct. Biol. 2018, 51, 19-27, 10.1016/j.sbi.2018.02.003

Enzymes are biomacromolecules with three-dimensional structures composed of peptide polymers via supramolecular interactions. Owing to the incredible catalytic efficiency and unique substrate selectivity, enzymes arouse considerable attention. To rival natural enzymes, various artificial enzymes have been developed over the last decades. Since supramolecular interactions play important roles in both substrate recognition and the process of enzymatic catalysis, designing artificial enzymes using supramolecular strategies is undoubtedly significant. Here we discuss the recent advances in constructing artificial enzymes using supramolecular platforms.

Cardona, F.; Goti, A.; Messori, L.

ChemCatChem 2017, 9, 4225-4230, 10.1002/cctc.201701083

A new green method for the preparation of nitrones through the aerobic oxidation of the corresponding N,N‐disubstituted hydroxylamines has been developed upon exploring the catalytic activity of a diruthenium catalyst, that is, [Ru2(OAc)4Cl]), in aqueous or alcoholic solution under mild reaction conditions (0.1 to 1 mol % catalyst, air, 50 °C) and reasonable reaction times. Notably, the catalytic activity of the dimetallic centre is retained after its binding to the small protein lysozyme. Interestingly, this new artificial metalloenzyme conferred complete chemoselectivity to the oxidation of cyclic hydroxylamines, in contrast to the diruthenium catalyst.

Fujieda, N.; Ward, T.R.

Chem. Sci. 2015, 6, 4060-4065, 10.1039/c5sc01065a

Adding a metal cofactor to a protein bearing a latent metal binding site endows the macromolecule with nascent catalytic activity.