Lu, Y.

Science 2018, 361, 1098-1101, 10.1126/science.aat8474

Multielectron redox reactions often require multicofactor metalloenzymes to facilitate coupled electron and proton movement, but it is challenging to design artificial enzymes to catalyze these important reactions, owing to their structural and functional complexity. We report a designed heteronuclear heme-[4Fe-4S] cofactor in cytochrome c peroxidase as a structural and functional model of the enzyme sulfite reductase. The initial model exhibits spectroscopic and ligand-binding properties of the native enzyme, and sulfite reduction activity was improved—through rational tuning of the secondary sphere interactions around the [4Fe-4S] and the substrate-binding sites—to be close to that of the native enzyme. By offering insight into the requirements for a demanding six-electron, seven-proton reaction that has so far eluded synthetic catalysts, this study provides strategies for designing highly functional multicofactor artificial enzymes.

Cavazza, C.; Ménage, S.

Angew. Chem. Int. Ed. 2013, 52, 3922-3925, 10.1002/anie.201209021

The substrate for an artificial iron monooxygenase was selected by using docking calculations. The high catalytic efficiency of the reported enzyme for sulfide oxidation was directly correlated to the predicted substrate binding mode in the protein cavity, thus illustrating the synergetic effect of the substrate binding site, protein scaffold, and catalytic site.

Bian, H.-D.; Huang, F.-P.

RSC Adv. 2016, 6, 44154-44162, 10.1039/C6RA08153C

Enantioselective oxidation of a series of alkyl aryl sulfides catalyzed by a novel VIV8 cluster is tested in an aqueous medium in the presence of serum albumin. The procedure is simple, environmentally friendly, selective, and highly reactive.

Sheldon, R.A.

Chem. Commun. 1998, 1891-1892, 10.1039/a804702b

Phytase (E.C. 3.1.3.8), which in vivo mediates the hydrolysis of phosphate esters, catalyses the enantioselective oxidation of thioanisole with H2O2, both in the presence and absence of vanadate ion, affording the S-sulfoxide in up to 66% ee at 100% conversion.

Ward, T.R.

J. Organomet. Chem. 2009, 694, 930-936, 10.1016/j.jorganchem.2008.11.023

Incorporation of achiral biotinylated manganese-salen complexes into streptavidin yields artificial metalloenzymes for aqueous sulfoxidation using hydrogen peroxide. Four biotinylated salen ligands were synthesized and their manganese complexes were tested in combination with several streptavidin mutants, yielding moderate conversions (up to 56%) and low enantioselectivities (maximum of 13% ee) for the sulfoxidation of thioanisole.

Sheldon, R.A.

Biotechnol. Bioeng. 2000, 67, 87-96, 10.1002/(SICI)1097-0290(20000105)67:1<87::AID-BIT10>3.0.CO;2-8

A semisynthetic peroxidase was designed by exploiting the structural similarity of the active sites of vanadium dependent haloperoxidases and acid phosphatases. Incorporation of vanadate ion into the active site of phytase (E.C. 3.1.3.8), which mediates in vivo the hydrolysis of phosphate esters, leads to the formation of a semisynthetic peroxidase, which catalyzes the enantioselective oxidation of prochiral sulfides with H2O2 affording the S‐sulfoxide, e.g. in 66% ee at 100% conversion for thioanisole. Under reaction conditions the semi‐synthetic vanadium peroxidase is stable for over 3 days with only a slight decrease in turnover frequency. Polar water‐miscible cosolvents, such as methanol, dioxane, and dimethoxyethane, can be used in concentrations of 30% (v/v) at a small penalty in activity and enantioselectivity. Among the transition metal oxoanions that are known to be potent inhibitors, only vanadate resulted in a semisynthetic peroxidase when incorporated into phytase. A number of other acid phosphatases and hydrolases were tested for peroxidase activity, when incorporated with vanadate ion. Phytases from Aspergillus ficuum, A. fumigatus, and A. nidulans, sulfatase from Helix pomatia, and phospholipase D from cabbage catalyzed enantioselective oxygen transfer reactions when incorporated with vanadium. However, phytase from A. ficuum was unique in also catalyzing the enantioselective sulfoxidation, albeit at a lower rate, in the absence of vanadate ion.

Sheldon, R.A.

Top. Catal. 2000, 13, 259-265, 10.1023/A:1009094619249

Approaches to the rational design of vanadium-based biocatalytic and biomimetic model systems as catalysts for enantioselective oxidations are reviewed. Incorporation of vanadate ion into the active site of phytase (E.C. 3.1.3.8), which in vivo mediates the hydrolysis of phosphate esters, afforded a relatively stable and inexpensive semi-synthetic peroxidase. It catalysed the enantioselective oxidation of prochiral sulfides with H2O2 affording the S-sulfoxide, e.g., in 68% ee at 100% conversion for thioanisole. Amongst the transition metal oxoanions that are known to be potent inhibitors of phosphatases, only vanadate resulted in a semi-synthetic peroxidase, when incorporated into phytase. In a biomimetic approach, vanadium complexes of chiral Schiff's base complexes were encapsulated in the super cages of a hydrophobic zeolite Y. Unfortunately, these ship-in-a-bottle complexes afforded only racemic sulfoxide in the catalytic oxidation of thioanisole with H2O2.