Lombardi, A.; Louro, R.O.

Chem. Commun. 2021, 57, 990-993, 10.1039/d0cc06676a

Fe-Mimochrome VI*a is a synthetic peroxidase and peroxygenase, featuring two different peptides that are covalently-linked to deuteroheme. To perform a systematic structure/function correlation, we purposely shortened the distance between the distal peptide and the heme, allowing for the separation and characterization of two regioisomers. They differ in both His axial-ligand orientation, as determined by paramagnetic NMR shifts, and activity. These findings highlight that synthetic metalloenzymes may provide an efficient tool for disentangling the role of axial ligand orientation over peroxidase activity.

Mahy, J.-P.; Ricoux, R.

ChemBioChem 2012, 13, 240-251, 10.1002/cbic.201100659

Enantioselective epoxidation: An artificial metalloenzyme obtained by noncovalent insertion of MnIII‐meso‐tetrakis(para‐carboxyphenyl)porphyrin Mn(TpCPP) into xylanase 10A from Streptomyces lividans as a host protein was able to catalyse the oxidation of para‐methoxystyrene by KHSO5 with a 16 % yield and the best enantioselectivity (80 % in favour of the R isomer) ever reported for an artificial metalloenzyme.

Kazlauskas, R.J.

Chem. - Eur. J. 2006, 12, 1587-1596, 10.1002/chem.200501413

Carbonic anhydrase is a zinc metalloenzyme that catalyzes the hydration of carbon dioxide to bicarbonate. Replacing the active‐site zinc with manganese yielded manganese‐substituted carbonic anhydrase (CA[Mn]), which shows peroxidase activity with a bicarbonate‐dependent mechanism. In the presence of bicarbonate and hydrogen peroxide, (CA[Mn]) catalyzed the efficient oxidation of o‐dianisidine with kcat/KM=1.4×106 m−1 s−1, which is comparable to that for horseradish peroxidase, kcat/KM=57×106 m−1 s−1. CA[Mn] also catalyzed the moderately enantioselective epoxidation of olefins to epoxides (E=5 for p‐chlorostyrene) in the presence of an amino‐alcohol buffer, such as N,N‐bis(2‐hydroxyethyl)‐2‐aminoethanesulfonic acid (BES). This enantioselectivity is similar to that for natural heme‐based peroxidases, but has the advantage that CA[Mn] avoids the formation of aldehyde side products. CA[Mn] degrades during the epoxidation limiting the yield of the epoxidations to <12 %. Replacement of active‐site residues Asn62, His64, Asn67, Gln92, or Thr200 with alanine by site‐directed mutagenesis decreased the enantioselectivity demonstrating that the active site controls the enantioselectivity of the epoxidation.

Lewis, J.C.

Tetrahedron 2014, 70, 4245-4249, 10.1016/j.tet.2014.03.008

New catalysts for non-directed hydrocarbon functionalization have great potential in organic synthesis. We hypothesized that incorporating a Mn-terpyridine cofactor into a protein scaffold would lead to artificial metalloenzymes (ArMs) in which the selectivity of the Mn cofactor could be controlled by the protein scaffold. We designed and synthesized a maleimide-substituted Mn-terpyridine cofactor and demonstrated that this cofactor could be incorporated into two different scaffold proteins to generate the desired ArMs. The structure and reactivity of one of these ArMs was explored, and the broad oxygenation capability of the Mn-terpyridine catalyst was maintained, providing a robust platform for optimization of ArMs for selective hydrocarbon functionalization.

Mahy, J.-P.

Tetrahedron: Asymmetry 2010, 21, 1593-1600, 10.1016/j.tetasy.2010.03.050

New anionic metalloporphyrin–estradiol conjugates have been synthesized and fully characterized, and have been further associated to a monoclonal anti-estradiol antibody 7A3, to generate new artificial metalloenzymes following the so-called ‘Trojan Horse’ strategy. The spectroscopic characteristics and dissociation constants of these complexes were similar to those obtained for the artificial metalloproteins obtained by association of cationic metalloporphyrin–estradiol conjugates to 7A3. This demonstrates that the nature of the porphyrin substituents, anionic or cationic, had little influence on the association with the antibody that is mainly driven by the tight association of the estradiol anchor with the binding pocket of the antibody. These new biocatalysts appeared to have an interesting catalytic activity in oxidation reactions. The iron(III)–anionic-porphyrin–estradiol-antibody complexes were found able to catalyze the chemoselective and slightly enantioselective (ee = 10%) sulfoxidation of sulfides by H2O2. The Mn(III)–porphyrin–estradiol-antibody complexes were found to catalyze the oxidation of styrene by KHSO5, the Mn(III)–cationic-porphyrin–estradiol-antibody complexes even showing the highest yields so far reported for the oxidation of styrene catalyzed by artificial metalloproteins. However, a lack of chemoselectivity and enantioselectivity was observed, which was probably due to a weak interaction of the metalloporphyrin cofactor with the binding pocket of antibody 7A3, as suggested by the similar UV–visible characteristics and catalytic activities obtained with both anionic and cationic porphyrins.

Reetz, M.T.

Chimia 2002, 56, 721-723, 10.2533/000942902777679920

The first step in applying the recently proposed concept concerning the application of directed evolution to the creation of selective hybrid catalysts is described, specifically the covalent attachment of Mn-salen moieties and of Cu-, Pd-, and Rh-complexes of dipyridine derivatives as well as the implantation of a diphosphine moiety in a protein, future steps being cycles of mutagenesis/screening.

Soumillion, P.

ChemBioChem 2006, 7, 1013-1016, 10.1002/cbic.200600127

Enantioselective epoxidation of styrene was observed in the presence of manganese‐containing carbonic anhydrase as catalyst. The probable oxygen‐transfer reagent is peroxymonocarbonate, which has a structural similarity with the hydrogenocarbonate substrate of the natural reaction. Styrene was chosen as the enzyme possesses a small hydrophobic cavity close to the active site.