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.

Hu, X.; Shima, S.

Angew. Chem. Int. Ed. 2021, 60, 13350-13357, 10.1002/anie.202100443

The reconstitution of [Mn]-hydrogenases using a series of MnI complexes is described. These complexes are designed to have an internal base or pro-base that may participate in metal–ligand cooperative catalysis or have no internal base or pro-base. Only MnI complexes with an internal base or pro-base are active for H2 activation; only [Mn]-hydrogenases incorporating such complexes are active for hydrogenase reactions. These results confirm the essential role of metal–ligand cooperation for H2 activation by the MnI complexes alone and by [Mn]-hydrogenases. Owing to the nature and position of the internal base or pro-base, the mode of metal–ligand cooperation in two active [Mn]-hydrogenases is different from that of the native [Fe]-hydrogenase. One [Mn]-hydrogenase has the highest specific activity of semi-synthetic [Mn]- and [Fe]-hydrogenases. This work demonstrates reconstitution of active artificial hydrogenases using synthetic complexes differing greatly from the native active site.

Arseniyadis, S.; Campagne, J.; Smietana, M.

Chem. Eur. J. 2020, 26, 3519-3523, 10.1002/chem.202000516

While artificial cyclases hold great promise in chemical synthesis, this work presents the first example of a DNA-catalyzed inverse electron-demand hetero-Diels–Alder (IEDHDA) between dihydrofuran and various α,β-unsaturated acyl imidazoles. The resulting fused bicyclic O,O-acetals containing three contiguous stereogenic centers are obtained in high yields (up to 99 %) and excellent diastereo- (up to >99:1 dr) and enantioselectivities (up to 95 % ee) using a low catalyst loading. Most importantly, these results show that the concept of DNA-based asymmetric catalysis can be expanded to new synthetic transformations offering an efficient, sustainable, and highly selective tool for the construction of chiral building blocks.

Ueno, T.

Chem. Commun. 2011, 47, 2074, 10.1039/C0CC03015E

We have constructed a robust β-helical nanotube from the component proteins of bacteriophage T4 and modified this nanotube with RuII(bpy)3 and ReI(bpy)(CO)3Cl complexes. The photocatalytic system arranged on the tube catalyzes the reduction of CO2 with higher reactivity than that of the mixture of the monomeric forms.

Ward, T.R.

Chem. Sci. 2018, 9, 5383-5388, 10.1039/c8sc00484f

Artificial metalloenzymes (ArMs hereafter) combine attractive features of both homogeneous catalysts and enzymes and offer the potential to implement new-to-nature reactions in living organisms. Herein we present an E. coli surface display platform for streptavidin (Sav hereafter) relying on an Lpp-OmpA anchor. The system was used for the high throughput screening of a bioorthogonal CpRu-based artificial deallylase (ADAse) that uncages an allylcarbamate-protected aminocoumarin 1. Two rounds of directed evolution afforded the double mutant S112M–K121A that displayed a 36-fold increase in surface activity vs. cellular background and a 5.7-fold increased in vitro activity compared to the wild type enzyme. The crystal structure of the best ADAse reveals the importance of mutation S112M to stabilize the cofactor conformation inside the protein.

Ward, T.R.

ACS Catal. 2016, 6, 3553-3557, 10.1021/acscatal.6b00258

NADH mimics (mNADHs) have been shown to accelerate and orthogonally activate ene reductase-catalyzed reactions. However, existing regeneration methods of NAD(P)H fail for mNADHs. Catalysis with artificial metalloenzymes based on streptavidin (Sav) variants and a biotinylated iridium cofactor enable mNADH regeneration with formate. This regeneration can be coupled with ene reductase-catalyzed asymmetric reduction of α,β-unsaturated compounds, because of the protective compartmentalization of the organometallic cofactor. With 10 mol % mNAD+, a preparative scale reaction (>100 mg) gave full conversion with 98% ee, where TTNs reached 2000, with respect to the Ir cofactor under ambient atmosphere in aqueous medium.

Hilvert, D.; Jiménez-Osés, G.

Nat. Chem. 2021, 13, 231-235, 10.1038/s41557-020-00628-4

New enzyme catalysts are usually engineered by repurposing the active sites of natural proteins. Here we show that design and directed evolution can be used to transform a non-natural, functionally naive zinc-binding protein into a highly active catalyst for an abiological hetero-Diels–Alder reaction. The artificial metalloenzyme achieves >104 turnovers per active site, exerts absolute control over reaction pathway and product stereochemistry, and displays a catalytic proficiency (1/KTS = 2.9 × 1010 M−1) that exceeds all previously characterized Diels–Alderases. These properties capitalize on effective Lewis acid catalysis, a chemical strategy for accelerating Diels–Alder reactions common in the laboratory but so far unknown in nature. Extension of this approach to other metal ions and other de novo scaffolds may propel the design field in exciting new directions.

Hromadová, M.

J. Electroanal. Chem. 2020, 859, 113882, 10.1016/j.jelechem.2020.113882

Electrochemical properties were studied for [(η6-arene)Ru(1,10-phenanthroline)Cl]Cl (arene = C6H5(CH2)2NHCOCH2Cl) organometallic complex 1, protein Papain PAP and its conjugate with organometallic complex 1-PAP. The latter can serve as an artificial metalloenzyme with catalytic activity in transfer hydrogenation. This work demonstrates that AC voltammetry and electrochemical impedance spectroscopy can be used as fast tools to screen the catalytic ability of 1-PAP electrochemically by studies of the catalytic hydrogen evolution reaction (HER). Proteins are known to catalyze this process, but we have shown that additional HER signal associated with the catalytic activity of 1 is observed for its conjugate with Papain 1-PAP.

Luk, L.Y.P.

RSC Adv. 2020, 10, 16147-16161, 10.1039/d0ra01526a

In this review, the development of organocatalytic artificial enzymes will be discussed. This area of protein engineering research has underlying importance, as it enhances the biocompatibility of organocatalysis for applications in chemical and synthetic biology research whilst expanding the catalytic repertoire of enzymes. The approaches towards the preparation of organocatalytic artificial enzymes, techniques used to improve their performance (selectivity and reactivity) as well as examples of their applications are presented. Challenges and opportunities are also discussed.

Roelfes, G.

Angew. Chem. Int. Ed. 2012, 51, 7472-7475, 10.1002/anie.201202070

A game of two halves: Artificial metalloenzymes are generated by forming a novel active site on the dimer interface of the transcription factor LmrR. Two copper centers are incorporated by binding to ligands in each half of the dimer. With this system up to 97 % ee was obtained in the benchmark CuII catalyzed Diels–Alder reaction (see scheme).

Li, C.

ACS Catal. 2020, 10, 6561-6567, 10.1021/acscatal.0c01203

Developing high-performance DNA-based biocatalysts for desired stereoselective syntheses remains a formidable challenge. Here, we report promising DNA-based catalysts comprised of G-quadruplex (G4) and Fe porphyrin for asymmetric olefin cyclopropanation. After the G4-based catalysts are optimized by several rounds of site mutation, their catalytic enantioselectivities achieve +81% and −86% enantiomeric excess (eetrans) at a turnover number (TON) as high as 500. The Fe porphyrin, binding upon the 5′,3′-end G-quartet, constitutes the active center for olefin cyclopropanation via an iron porphyrin carbene intermediate. The findings provide an opportunity for generating high-value chiral cyclopropane blocks via G4 biocatalysts and shed light on the potential of DNA as protein enzymes for catalysis.

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.

Salmain, M.

Chem. Commun. 2012, 48, 11984, 10.1039/c2cc36980j

Artificial metalloproteins resulting from the embedding of half-sandwich Ru(II)/Rh(III) fatty acid derivatives within β-lactoglobulin catalysed the asymmetric transfer hydrogenation of trifluoroacetophenone with modest to good conversions and fair ee's.

Fasan, R.

Curr. Opin. Green Sustain. Chem. 2021, 31, 100494, 10.1016/j.cogsc.2021.100494

The direct functionalization of C–H bonds constitutes a powerful strategy to construct and diversify organic molecules. However, controlling the chemo- and site-selectivity of this transformation, particularly in complex molecular settings, represents a significant challenge. Metalloenzymes are ideal platforms for achieving catalyst-controlled selective C–H bond functionalization as their reactivities can be tuned by protein engineering and/or redesign of their cofactor environment. In this review, we highlight recent progress in the development of engineered and artificial metalloenzymes for C–H functionalization, with a focus on biocatalytic strategies for selective C–H oxyfunctionalization and halogenation as well as C–H amination and C–H carbene insertion via abiological nitrene and carbene transfer chemistries. Engineered heme and nonheme iron dependent enzymes have emerged as promising scaffolds for executing these transformations with high chemo-, regio-, and stereocontrol as well as tunable selectivity. These emerging systems and methodologies have expanded the toolbox of sustainable strategies for organic synthesis and created new opportunities for the generation of chiral building blocks, the late-stage C–H functionalization of complex molecules, and the total synthesis of natural products.

Green, A.P.; Hilvert, D.

Chem. - Eur. J. 2018, 24, 11821-11830, 10.1002/chem.201800975

Nature employs a limited number of genetically encoded, metal‐coordinating residues to create metalloenzymes with diverse structures and functions. Engineered components of the cellular translation machinery can now be exploited to encode non‐canonical ligands with user‐defined electronic and structural properties. This ability to install “chemically programmed” ligands into proteins can provide powerful chemical probes of metalloenzyme mechanism and presents excellent opportunities to create metalloprotein catalysts with augmented properties and novel activities. In this Concept article, we provide an overview of several recent studies describing the creation of engineered metalloenzymes with interesting catalytic properties, and reveal how characterization of these systems has advanced our understanding of nature's bioinorganic mechanisms. We also highlight how powerful laboratory evolution protocols can be readily adapted to allow optimization of metalloenzymes with non‐canonical ligands. This approach combines beneficial features of small molecule and protein catalysis by allowing the installation of a greater variety of local metal coordination environments into evolvable protein scaffolds, and holds great promise for the future creation of powerful metalloprotein catalysts for a host of synthetically valuable transformations.

Craik, C.S.

Biochemistry 1995, 34, 2172-2180, 10.1021/bi00007a010

Histidine substrate specificity has been engineered into trypsin by creating metal binding sites for Ni2+ and Zn2+ ions. The sites bridge the substrate and enzyme on the leaving-group side of the scissile bond. Application of simple steric and geometric criteria to a crystallographically derived enzyme- substrate model suggested that histidine specificity at the P2' position might be acheived by a tridentate site involving amino acid residues 143 and 151 of trypsin. Trypsin N143H/E151H hydrolyzes a P2'- His-containing peptide (AGPYAHSS) exclusively in the presence of nickel or zinc with a high level of catalytic efficiency. Since cleavage following the tyrosine residue is normally highly disfavored by trypsin, this result demonstrates that a metal cofactor can be used to modulate specificity in a designed fashion. The same geometric criteria applied in the primary SI binding pocket suggested that the single-site mutation D189H might effect metal-dependent His specificity in trypsin. However, kinetic and crystallographic analysis of this variant showed that the design was unsuccessful because His 189 rotates away from substrate causing a large perturbation in adjacent surface loops. This observation suggests that the reason specificity modification at the trypsin S1 site requires extensive mutagenesis is because the pocket cannot deform locally to accommodate alternate PI side chains. By taking advantage of the extended subsites, an alternate substrate specificity has been engineered into trypsin.

Lewis, J.C.

Nat. Commun. 2015, 6, 10.1038/ncomms8789

Artificial metalloenzymes (ArMs) formed by incorporating synthetic metal catalysts into protein scaffolds have the potential to impart to chemical reactions selectivity that would be difficult to achieve using metal catalysts alone. In this work, we covalently link an alkyne-substituted dirhodium catalyst to a prolyl oligopeptidase containing a genetically encoded L-4-azidophenylalanine residue to create an ArM that catalyses olefin cyclopropanation. Scaffold mutagenesis is then used to improve the enantioselectivity of this reaction, and cyclopropanation of a range of styrenes and donor–acceptor carbene precursors were accepted. The ArM reduces the formation of byproducts, including those resulting from the reaction of dirhodium–carbene intermediates with water. This shows that an ArM can improve the substrate specificity of a catalyst and, for the first time, the water tolerance of a metal-catalysed reaction. Given the diversity of reactions catalysed by dirhodium complexes, we anticipate that dirhodium ArMs will provide many unique opportunities for selective catalysis.

Sauer, D.F.; Schwaneberg, U.

Nat. Catal. 2021, 4, 814-827, 10.1038/s41929-021-00673-3

The field of artificial metalloenzymes (ArMs) is rapidly growing and ArMs are attracting increasing attention, for example, in the fields of biosensing and drug therapy. Protein-engineering methods that are commonly used to tailor the properties of natural enzymes are more frequently included in the design of ArMs. In particular, directed evolution allows the fine-tuning of ArMs, ultimately assisting in the development of their enormous potential. The integration of ArMs in whole cells enables their in vivo application and facilitates high-throughput directed-evolution methodologies. In this Review, we highlight the recent progress of whole-cell conversions and applications of ArMs and critically discuss their limitations and prospects. To focus on ArMs and their specific properties, advantages and challenges, the evolution of natural enzymes for non-natural reactions will not be covered.

Lewis, J.C.; Roux, B.

Angew. Chem. Int. Ed. 2021, 60, 23672-23677, 10.1002/anie.202107982

Artificial metalloenzymes (ArMs) are commonly used to control the stereoselectivity of catalytic reactions, but controlling chemoselectivity remains challenging. In this study, we engineer a dirhodium ArM to catalyze diazo cross-coupling to form an alkene that, in a one-pot cascade reaction, is reduced to an alkane with high enantioselectivity (typically >99 % ee) by an alkene reductase. The numerous protein and small molecule components required for the cascade reaction had minimal effect on ArM catalysis. Directed evolution of the ArM led to improved yields and E/Z selectivities for a variety of substrates, which translated to cascade reaction yields. MD simulations of ArM variants were used to understand the structural role of the cofactor on ArM conformational dynamics. These results highlight the ability of ArMs to control both catalyst stereoselectivity and chemoselectivity to enable reactions in complex media that would otherwise lead to undesired side reactions.

Jarvis, A.G.

ACS Catal. 2021, 11, 3620-3627, 10.1021/acscatal.0c05413

Protein engineering has shown widespread use in improving the industrial application of enzymes and broadening the conditions they are able to operate under by increasing their thermostability and solvent tolerance. Here, we show that protein engineering can be used to increase the thermostability of an artificial metalloenzyme. Thermostable variants of the human steroid carrier protein 2L, modified to bind a metal catalyst, were created by rational design using structural data and a 3DM database. These variants were tested to identify mutations that enhanced the stability of the protein scaffold, and a significant increase in melting temperature was observed with a number of modified metalloenzymes. The ability to withstand higher reaction temperatures resulted in an increased activity in the hydroformylation of 1-octene, with more than fivefold improvement in turnover number, whereas the selectivity for linear aldehyde remained high up to 80%.

Chem. Eur. J. 2020, 26, 6240-6246, 10.1002/chem.202000204

Hybrid protein–organometallic catalysts are being explored for selective catalysis of a number of reactions, because they utilize the complementary strengths of proteins and of organometallic complex. Herein, we present an artificial hydrogenase, StrepH2, built by incorporating a biotinylated [Fe–Fe] hydrogenase organometallic mimic within streptavidin. This strategy takes advantage of the remarkable strength and specificity of biotin-streptavidin recognition, which drives quantitative incorporation of the biotinylated diironhexacarbonyl center into streptavidin, as confirmed by UV/Vis spectroscopy and X-ray crystallography. FTIR spectra of StrepH2 show characteristic peaks at shift values indicative of interactions between the catalyst and the protein scaffold. StrepH2 catalyzes proton reduction to hydrogen in aqueous media during photo- and electrocatalysis. Under photocatalytic conditions, the protein-embedded catalyst shows enhanced efficiency and prolonged activity compared to the isolated catalyst. Transient absorption spectroscopy data suggest a mechanism for the observed increase in activity underpinned by an observed longer lifetime for the catalytic species FeIFe0 when incorporated within streptavidin compared to the biotinylated catalyst in solution.

Jarvis, A.G.; Kamer, P.C.J.

Angew. Chem. Int. Ed. 2017, 129, 13784-13788, 10.1002/ange.201705753

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.

Fasan, R.; Khare, S.D.

Proc. Natl. Acad. Sci. U. S. A. 2017, 114, 12472-12477, 10.1073/pnas.1708907114

Thermostabilization represents a critical and often obligatory step toward enhancing the robustness of enzymes for organic synthesis and other applications. While directed evolution methods have provided valuable tools for this purpose, these protocols are laborious and time-consuming and typically require the accumulation of several mutations, potentially at the expense of catalytic function. Here, we report a minimally invasive strategy for enzyme stabilization that relies on the installation of genetically encoded, nonreducible covalent staples in a target protein scaffold using computational design. This methodology enables the rapid development of myoglobin-based cyclopropanation biocatalysts featuring dramatically enhanced thermostability (ΔTm = +18.0 °C and ΔT50 = +16.0 °C) as well as increased stability against chemical denaturation [ΔCm (GndHCl) = 0.53 M], without altering their catalytic efficiency and stereoselectivity properties. In addition, the stabilized variants offer superior performance and selectivity compared with the parent enzyme in the presence of a high concentration of organic cosolvents, enabling the more efficient cyclopropanation of a water-insoluble substrate. This work introduces and validates an approach for protein stabilization which should be applicable to a variety of other proteins and enzymes.

Rimoldi, I.

ChemCatChem 2016, 8, 1665-1670, 10.1002/cctc.201600116

The possibility of obtaining an efficient artificial imine reductase was investigated by introducing a chiral cofactor into artificial metalloenzymes based on biotin–streptavidin technology. In particular, a chiral biotinylated 1,3‐diamine ligand in coordination with iridium(III) complex was developed. Optimized chemogenetic studies afforded positive results in the stereoselective reduction of a cyclic imine, the salsolidine precursor, as a standard substrate with access to both enantiomers. Various factors such as pH, temperature, number of binding sites, and steric hindrance of the catalytic moiety have been proved to affect both efficiency and enantioselectivity, underlining the great flexibility of this system in comparison with the achiral system. Computational studies were also performed to explain how the metal configuration, in the proposed system, might affect the observed stereochemical outcome.

Lewis, J.C.

Nat. Chem. 2018, 10, 318-324, 10.1038/nchem.2927

Random mutagenesis has the potential to optimize the efficiency and selectivity of protein catalysts without requiring detailed knowledge of protein structure; however, introducing synthetic metal cofactors complicates the expression and screening of enzyme libraries, and activity arising from free cofactor must be eliminated. Here we report an efficient platform to create and screen libraries of artificial metalloenzymes (ArMs) via random mutagenesis, which we use to evolve highly selective dirhodium cyclopropanases. Error-prone PCR and combinatorial codon mutagenesis enabled multiplexed analysis of random mutations, including at sites distal to the putative ArM active site that are difficult to identify using targeted mutagenesis approaches. Variants that exhibited significantly improved selectivity for each of the cyclopropane product enantiomers were identified, and higher activity than previously reported ArM cyclopropanases obtained via targeted mutagenesis was also observed. This improved selectivity carried over to other dirhodium-catalysed transformations, including N–H, S–H and Si–H insertion, demonstrating that ArMs evolved for one reaction can serve as starting points to evolve catalysts for others.

Ward, T.R.

ChemCatChem 2014, 6, 1010-1014, 10.1002/cctc.201300825

We report on the optimization of an artificial imine reductase based on the biotin‐streptavidin technology. With the aim of rapidly generating chemical diversity, a novel strategy for the formation and evaluation of biotinylated complexes is disclosed. Tethering the biotin‐anchor to the Cp* moiety leaves three free coordination sites on a d6 metal for the introduction of chemical diversity by coordination of a variety of ligands. To test the concept, 34 bidentate ligands were screened and a selection of the 6 best was tested in the presence of 21 streptavidin (Sav) isoforms for the asymmetric imine reduction by the resulting three legged piano stool complexes. Enantiopure α‐amino amides were identified as promising bidentate ligands: up to 63 % ee and 190 turnovers were obtained in the formation of 1‐phenyl‐1,2,3,4‐tetrahydroisoquinoline with [IrCp*biotin(L‐ThrNH2)Cl]⊂SavWT as a catalyst.

Wang, J.

Acc. Chem. Res. 2019, 52, 557-565, 10.1021/acs.accounts.8b00627

Many artificial enzymes that catalyze redox reactions have important energy, environmental, and medical applications. Native metalloenzymes use a set of redox-active amino acids and cofactors as redox centers, with a potential range between −700 and +800 mV versus standard hydrogen electrode (SHE, all reduction potentials are versus SHE). The redox potentials and the orientation of redox centers in native metalloproteins are optimal for their redox chemistry. However, the limited number and potential range of native redox centers challenge the design and optimization of novel redox chemistry in metalloenzymes. Artificial metalloenzymes use non-native redox centers and could go far beyond the natural range of redox potentials for novel redox chemistry. In addition to designing protein monomers, strategies for increasing the electron transfer rate in self-assembled protein complexes and protein–electrode or −nanomaterial interfaces will be discussed. Redox reactions in proteins occur on redox active amino acid residues (Tyr, Trp, Met, Cys, etc.) and cofactors (iron sulfur clusters, flavin, heme, etc.). The redox potential of these redox centers cover a ∼1.5 V range and is optimized for their specific functions. Despite recent progress, tuning the redox potential for amino acid residues or cofactors remains challenging. Many redox-active unnatural amino acids (UAAs) can be incorporated into protein via genetic codon expansion. Their redox potentials extend the range of physiologically relevant potentials. Indeed, installing new redox cofactors with fined-tuned redox potentials is essential for designing novel redox enzymes. By combining UAA and redox cofactor incorporation, we harnessed light energy to reduce CO2 in a fluorescent protein, mimicking photosynthetic apparatus in nature. Manipulating the position and reduction potential of redox centers inside proteins is important for optimizing the electron transfer rate and the activity of artificial enzymes. Learning from the native electron transfer complex, protein–protein interactions can be enhanced by increasing the electrostatic interaction between proteins. An artificial oxidase showed close to native enzyme activity with optimized interaction with electron transfer partner and increased electron transfer efficiency. In addition to the de novo design of protein–protein interaction, protein self-assembly methods using scaffolds, such as proliferating cell nuclear antigen, to efficiently anchor enzymes and their redox partners. The self-assembly process enhances electron transfer efficiency and enzyme activity by bringing redox centers into close proximity of each other. In addition to protein self-assembly, protein–electrode or protein–nanomaterial self-assembly can also promote efficient electron transfer from inorganic materials to enzyme active sites. Such hybrid systems combine the efficiency of enzyme reactions and the robustness of electrodes or nanomaterials, often with advantageous catalytic activities. By combining these strategies, we can not only mimic some of nature’s most fascinating reactions, such as photosynthesis and aerobic respiration, but also transcend nature toward environmental, energy, and health applications.

Arnold, F.H.; Fasan, R.

Curr. Opin. Biotechnol. 2017, 47, 102-111, 10.1016/j.copbio.2017.06.005

The surge in reports of heme-dependent proteins as catalysts for abiotic, synthetically valuable carbene and nitrene transfer reactions dramatically illustrates the evolvability of the protein world and our nascent ability to exploit that for new enzyme chemistry. We highlight the latest additions to the hemoprotein-catalyzed reaction repertoire (including carbene Si–H and C–H insertions, Doyle–Kirmse reactions, aldehyde olefinations, azide-to-aldehyde conversions, and intermolecular nitrene C–H insertion) and show how different hemoprotein scaffolds offer varied reactivity and selectivity. Preparative-scale syntheses of pharmaceutically relevant compounds accomplished with these new catalysts are beginning to demonstrate their biotechnological relevance. Insights into the determinants of enzyme lifetime and product yield are providing generalizable cues for engineering heme-dependent proteins to further broaden the scope and utility of these non-natural activities.

Ward, T.R.

Chimia 2003, 57, 586-588, 10.2533/000942903777678722

With the aim of exploring the role of the second coordination sphere in enantioselective catalysis, achiral organometallic catalyst precursors are anchored in proteins via non-covalent interactions. A chemogenetic procedure allows the activity and the enantioselectivity of the artificial metalloenzymes to be optimized, to yield hybrid catalysts with features reminiscent both of enzymatic and homogeneous catalysts.