126 publications

126 publications

8-Amino-5,6,7,8-tetrahydroquinoline in Iridium(III) Biotinylated Cp* Complex as Artificial Imine Reductase

Rimoldi, I.

New J. Chem. 2018, 42, 18773-18776, 10.1039/C8NJ04558E

The imine reductase formed by the (R)-CAMPY ligand bound to the S112M Sav mutant showed an 83% ee in the asymmetric transfer hydrogenation of 6,7-dimethoxy-1-methyl-3,4-dihydroisoquinoline.


Metal: Ir
Ligand type: Cp*; Diamine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 32
ee: 83
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Cp*; Diamine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 99
ee: 13
PDB: ---
Notes: ---

A Cell-Penetrating Artificial Metalloenzyme Regulates a Gene Switch in a Designer Mammalian Cell

Fussenegger, M.; Matile, S.; Ward, T.R.

Nat. Commun. 2018, 9, 10.1038/s41467-018-04440-0

Complementing enzymes in their native environment with either homogeneous or heterogeneous catalysts is challenging due to the sea of functionalities present within a cell. To supplement these efforts, artificial metalloenzymes are drawing attention as they combine attractive features of both homogeneous catalysts and enzymes. Herein we show that such hybrid catalysts consisting of a metal cofactor, a cell-penetrating module, and a protein scaffold are taken up into HEK-293T cells where they catalyze the uncaging of a hormone. This bioorthogonal reaction causes the upregulation of a gene circuit, which in turn leads to the expression of a nanoluc-luciferase. Relying on the biotin–streptavidin technology, variation of the biotinylated ruthenium complex: the biotinylated cell-penetrating poly(disulfide) ratio can be combined with point mutations on streptavidin to optimize the catalytic uncaging of an allyl-carbamate-protected thyroid hormone triiodothyronine. These results demonstrate that artificial metalloenzymes offer highly modular tools to perform bioorthogonal catalysis in live HEK cells.


Metal: Ru
Ligand type: Cp; Quinoline
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Genetic
Reaction: Deallylation
Max TON: 33
ee: ---
PDB: ---
Notes: ---

Achiral Cyclopentadienone Iron Tricarbonyl Complexes Embedded in Streptavidin: An Access to Artificial Iron Hydrogenases and Application in Asymmetric Hydrogenation

Renaud, J.-L.; Ward, T.R.

Catal. Lett. 2016, 146, 564-569, 10.1007/s10562-015-1681-6

We report on the synthesis of biotinylated (cyclopentadienone)iron tricarbonyl complexes, the in situ generation of the corresponding streptavidin conjugates and their application in asymmetric hydrogenation of imines and ketones.


Metal: Fe
Ligand type: CO; Cyclopentadienone
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Hydrogenation
Max TON: 20
ee: 34
PDB: ---
Notes: ---

Addressable DNA–Myoglobin Photocatalysis

Niemeyer, C.M.

Chem. - Asian J. 2009, 4, 1064-1069, 10.1002/asia.200900082

A hybrid myoglobin, containing a single‐stranded DNA anchor and a redox‐active ruthenium moiety tethered to the heme center can be used as a photocatalyst. The catalyst can be selectively immobilized on a surface‐bound complementary DNA molecule and thus readily recycled from complex reaction mixtures. This principle may be applied to a range of heme‐dependent enzymes allowing the generation of novel light‐triggered photocatalysts. Photoactivatable myoglobin containing a DNA oligonucleotide as a structural anchor was designed by using the reconstitution of artificial heme moieties containing Ru3+ ions. This semisynthetic DNA–enzyme conjugate was successfully used for the oxidation of peroxidase substrates by using visible light instead of H2O2 for the activation. The DNA anchor was utilized for the immobilization of the enzyme on the surface of magnetic microbeads. Enzyme activity measurements not only indicated undisturbed biofunctionality of the tethered DNA but also enabled magnetic separation‐based enrichment and recycling of the photoactivatable biocatalyst.


Metal: Ru
Ligand type: Bipyridine
Host protein: Myoglobin (Mb)
Anchoring strategy: Supramolecular
Optimization: ---
Reaction: Photooxidation
Max TON: ---
ee: ---
PDB: ---
Notes: Horse heart myoglobin

A Dual Anchoring Strategy for the Localization and Activation of Artificial Metalloenzymes Based on the Biotin−Streptavidin Technology

Ward, T.R.

J. Am. Chem. Soc. 2013, 135, 5384-5388, 10.1021/ja309974s

Artificial metalloenzymes result from anchoring an active catalyst within a protein environment. Toward this goal, various localization strategies have been pursued: covalent, supramolecular, or dative anchoring. Herein we show that introduction of a suitably positioned histidine residue contributes to firmly anchor, via a dative bond, a biotinylated rhodium piano stool complex within streptavidin. The in silico design of the artificial metalloenzyme was confirmed by X-ray crystallography. The resulting artificial metalloenzyme displays significantly improved catalytic performance, both in terms of activity and selectivity in the transfer hydrogenation of imines. Depending on the position of the histidine residue, both enantiomers of the salsolidine product can be obtained.


Metal: Ir
Ligand type: Amino acid; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: 14
ee: 11
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Amino acid; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: 100
ee: 79
PDB: ---
Notes: ---

A Hydroxyquinoline‐Based Unnatural Amino Acid for the Design of Novel Artificial Metalloenzymes

Roelfes, G.

ChemBioChem 2020, 21, 3077-3081, 10.1002/cbic.202000306

We have examined the potential of the noncanonical amino acid (8-hydroxyquinolin-3-yl)alanine (HQAla) for the design of artificial metalloenzymes. HQAla, a versatile chelator of late transition metals, was introduced into the lactococcal multidrug-resistance regulator (LmrR) by stop codon suppression methodology. LmrR_HQAla was shown to complex efficiently with three different metal ions, CuII, ZnII and RhIII to form unique artificial metalloenzymes. The catalytic potential of the CuII-bound LmrR_HQAla enzyme was shown through its ability to catalyse asymmetric Friedel-Craft alkylation and water addition, whereas the ZnII-coupled enzyme was shown to mimic natural Zn hydrolase activity.


Metal: Cu
Ligand type: Hydroxyquinoline
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: 11
ee: 51
PDB: 3F8B
Notes: Also used Rh, but no reaction detected.

Metal: Cu
Ligand type: Hydroxyquinoline
Anchoring strategy: Supramolecular
Optimization: Genetic
Reaction: Water addition
Max TON: ---
ee: ---
PDB: 3F8B
Notes: ---

Metal: Zn
Ligand type: Hydroxyquinoline
Anchoring strategy: Supramolecular
Optimization: Genetic
Reaction: C-H activation
Max TON: ---
ee: ---
PDB: 3F8B
Notes: ---

Albumin-Conjugated Corrole Metal Complexes: Extremely Simple Yet Very Efficient Biomimetic Oxidation Systems

Gross, Z.

J. Am. Chem. Soc. 2005, 127, 2883-2887, 10.1021/ja045372c

An extremely simple biomimetic oxidation system, consisting of mixing metal complexes of amphiphilic corroles with serum albumins, utilizes hydrogen peroxide for asymmetric sulfoxidation in up to 74% ee. The albumin-conjugated manganese corroles also display catalase-like activity, and mechanistic evidence points toward oxidant-coordinated manganese(III) as the prime reaction intermediate.


Metal: Mn
Ligand type: Corrole
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Sulfoxidation
Max TON: 8
ee: 74
PDB: ---
Notes: ---

Metal: Mn
Ligand type: Corrole
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Sulfoxidation
Max TON: 42
ee: 52
PDB: ---
Notes: ---

Alternative Strategy to Obtain Artificial Imine Reductase by Exploiting Vancomycin/D-Ala-D-Ala Interactions with an Iridium Metal Complex

Pellegrino, S.; Rimoldi, I.

Inorg. Chem. 2021, 60, 2976-2982, 10.1021/acs.inorgchem.0c02969

Based on the supramolecular interaction between vancomycin (Van), an antibiotic glycopeptide, and D-Ala-D-Ala (DADA) dipeptides, a novel class of artificial metalloenzymes was synthesized and characterized. The presence of an iridium(III) ligand at the N-terminus of DADA allowed the use of the metalloenzyme as a catalyst in the asymmetric transfer hydrogenation of cyclic imines. In particular, the type of link between DADA and the metal-chelating moiety was found to be fundamental for inducing asymmetry in the reaction outcome, as highlighted by both computational studies and catalytic results. Using the [IrCp*(m-I)Cl]Cl ⊂ Van complex in 0.1 M CH3COONa buffer at pH 5, a significant 70% (S) e.e. was obtained in the reduction of quinaldine B.


Metal: Ir
Ligand type: Cp*; Diamine
Host protein: DADA dipeptide
Anchoring strategy: Supramolecular
Optimization: Chemical
Max TON: 50
ee: 70
PDB: ---
Notes: ---

An Artificial Cofactor Catalyzing the Baylis‐Hillman Reaction with Designed Streptavidin as Protein Host

Höcker, B.; Lechner, H.

ChemBioChem 2021, 22, 1573-1577, 10.1002/cbic.202000880

An artificial cofactor based on an organocatalyst embedded in a protein has been used to conduct the Baylis-Hillman reaction in a buffered system. As protein host, we chose streptavidin, as it can be easily crystallized and thereby supports the design process. The protein host around the cofactor was rationally designed on the basis of high-resolution crystal structures obtained after each variation of the amino acid sequence. Additionally, DFT-calculated intermediates and transition states were used to rationalize the observed activity. Finally, repeated cycles of structure determination and redesign led to a system with an up to one order of magnitude increase in activity over the bare cofactor and to the most active proteinogenic catalyst for the Baylis-Hillman reaction known today.


Metal: ---
Ligand type: ---
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Max TON: ---
ee: ---
PDB: 6T1E
Notes: Organocatalyst

An Artificial Heme Enzyme for Cyclopropanation Reactions

Roelfes, G.

Angew. Chem. Int. Ed. 2018, 57, 7785-7789, 10.1002/anie.201802946

An artificial heme enzyme was created through self‐assembly from hemin and the lactococcal multidrug resistance regulator (LmrR). The crystal structure shows the heme bound inside the hydrophobic pore of the protein, where it appears inaccessible for substrates. However, good catalytic activity and moderate enantioselectivity was observed in an abiological cyclopropanation reaction. We propose that the dynamic nature of the structure of the LmrR protein is key to the observed activity. This was supported by molecular dynamics simulations, which showed transient formation of opened conformations that allow the binding of substrates and the formation of pre‐catalytic structures.


Metal: Fe
Ligand type: Protoporphyrin IX
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Cyclopropanation
Max TON: 449
ee: 51
PDB: 6FUU
Notes: ---

An Artificial Imine Reductase Based on the Ribonuclease S Scaffold

Ward, T.R.

ChemCatChem 2014, 6, 736-740, 10.1002/cctc.201300995

Dative anchoring of a piano‐stool complex within ribonuclease S resulted in an artificial imine reductase. The catalytic performance was modulated upon variation of the coordinating amino acid residues in the S‐peptide. Binding of Cp*Ir (Cp*=C5Me5) to the native active site resulted in good conversions and moderate enantiomeric excess values for the synthesis of salsolidine.


Metal: Ir
Ligand type: Amino acid; Cp*
Host protein: Ribonuclease S
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: 4
ee: 18
PDB: ---
Notes: ---

An Artificial Metalloenzyme for Carbene Transfer Based on a Biotinylated Dirhodium Anchored Within Streptavidin

Ward, T.R.

Cat. Sci. Technol. 2018, 8, 2294-2298, 10.1039/C8CY00646F

We report an artificial carbenoid transferase which combines a biotinylated dirhodium moiety within streptavidin scaffold.


Metal: Rh
Ligand type: Carboxylate
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Cyclopropanation
Max TON: ~60
ee: ---
PDB: ---
Notes: Cyclopropanation reaction was also performed in the E. coli periplasm.

Metal: Rh
Ligand type: Carboxylate
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: C-H insertion
Max TON: ~60
ee: ---
PDB: ---
Notes: ---

An Artificial Oxygenase Built from Scratch: Substrate Binding Site Identified Using a Docking Approach

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.


Metal: Fe
Ligand type: BPMCN; BPMEN
Host protein: NikA
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: 199
ee: ≤5
PDB: ---
Notes: ---

An Enantioselective Artificial Suzukiase Based on the Biotin–Streptavidin Technology

Ward, T.R.

Chem. Sci. 2016, 7, 673-677, 10.1039/c5sc03116h

Introduction of a biotinylated monophosphine palladium complex within streptavidin affords an enantioselective artificial Suzukiase. Site-directed mutagenesis allowed the optimization of the activity and the enantioselectivity of this artificial metalloenzyme. A variety of atropisomeric biaryls were produced in good yields and up to 90% ee.


Metal: Pd
Ligand type: Allyl; Phosphine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 88
ee: 80
PDB: ---
Notes: ---

Metal: Pd
Ligand type: Allyl; Carbene
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 5
ee: ---
PDB: ---
Notes: ---

An NAD(P)H-Dependent Artificial Transfer Hydrogenase for Multienzymatic Cascades

Ward, T.R.

J. Am. Chem. Soc. 2016, 138, 5781-5784, 10.1021/jacs.6b02470

Enzymes typically depend on either NAD(P)H or FADH2 as hydride source for reduction purposes. In contrast, organometallic catalysts most often rely on isopropanol or formate to generate the reactive hydride moiety. Here we show that incorporation of a Cp*Ir cofactor possessing a biotin moiety and 4,7-dihydroxy-1,10-phenanthroline into streptavidin yields an NAD(P)H-dependent artificial transfer hydrogenase (ATHase). This ATHase (0.1 mol%) catalyzes imine reduction with 1 mM NADPH (2 mol%), which can be concurrently regenerated by a glucose dehydrogenase (GDH) using only 1.2 equiv of glucose. A four-enzyme cascade consisting of the ATHase, the GDH, a monoamine oxidase, and a catalase leads to the production of enantiopure amines.


Metal: Ir
Ligand type: Cp*; Phenanthroline
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: >999
ee: >99
PDB: ---
Notes: ---

A Noncanonical Proximal Heme Ligand Affords an Efficient Peroxidase in a Globin Fold

Green, A.P.; Hilvert, D.

J. Am. Chem. Soc. 2018, 140, 1535-1543, 10.1021/jacs.7b12621

Expanding the range of genetically encoded metal coordination environments accessible within tunable protein scaffolds presents excellent opportunities for the creation of metalloenzymes with augmented properties and novel activities. Here, we demonstrate that installation of a noncanonical Nδ-methyl histidine (NMH) as the proximal heme ligand in the oxygen binding protein myoglobin (Mb) leads to substantial increases in heme redox potential and promiscuous peroxidase activity. Structural characterization of this catalytically modified myoglobin variant (Mb NMH) revealed significant changes in the proximal pocket, including alterations to hydrogen-bonding interactions involving the prosthetic porphyrin cofactor. Further optimization of Mb NMH via a combination of rational modification and several rounds of laboratory evolution afforded efficient peroxidase biocatalysts within a globin fold, with activities comparable to those displayed by nature’s peroxidases.


Metal: Fe
Host protein: Myoglobin (Mb)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Oxidation
Max TON: ~1650
ee: ---
PDB: 5OJ9
Notes: Oxidation of amplex red

Antibody-Metalloporphyrin Catalytic Assembly Mimics Natural Oxidation Enzymes

Keinan, E.

J. Am. Chem. Soc. 1999, 121, 8978-8982, 10.1021/ja990314q

An antibody−metalloporphyrin assembly that catalyzes the enantioselective oxidation of aromatic sulfides to sulfoxides is presented. Antibody SN37.4 was elicited against a water-soluble tin(IV) porphyrin containing an axial α-naphthoxy ligand. The catalytic assembly comprising antibody SN37.4 and a ruthenium(II) porphyrin cofactor exhibited typical enzyme characteristics, such as predetermined oxidant and substrate selectivity, enantioselective delivery of oxygen to the substrate, and Michaelis−Menten saturation kinetics. This assembly, which promotes a complex, multistep catalytic event, represents a close model of natural heme-dependent oxidation enzymes.


Metal: Ru
Ligand type: Porphyrin
Host protein: Antibody SN37.4
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: 750
ee: 43
PDB: ---
Notes: ---

A Palladium-Catalyst Stabilized in the Chiral Environment of a Monoclonal Antibody in Water

Arada, H.; Yamaguchi, H.

Chem. Commun. 2020, 56, 1605-1607, 10.1039/c9cc08756g

We report the first preparation of a monoclonal antibody (mAb) that can immobilize a palladium (Pd)-complex. The allylic amination reaction using a supramolecular catalyst of the Pd-complex with mAb selectively gives the (R)-enantiomer product.


Metal: Pd
Ligand type: Allyl; Phosphine
Host protein: Antibody
Anchoring strategy: Supramolecular
Optimization: ---
Reaction: Allylic amination
Max TON: 600
ee: 98
PDB: ---
Notes: Recalculated TON

Aqueous Oxidation of Alcohols Catalyzed by Artificial Metalloenzymes Based on the Biotin–Avidin Technology

Ward, T.R.

J. Organomet. Chem. 2005, 690, 4488-4491, 10.1016/j.jorganchem.2005.02.001

Based on the incorporation of biotinylated organometallic catalyst precursors within (strept)avidin, we have developed artificial metalloenzymes for the oxidation of secondary alcohols using tert-butylhydroperoxide as oxidizing agent. In the presence of avidin as host protein, the biotinylated aminosulfonamide ruthenium piano stool complex 1 (0.4 mol%) catalyzes the oxidation of sec-phenethyl alcohol at room temperature within 90 h in over 90% yield. Gel electrophoretic analysis of the reaction mixture suggests that the host protein is not oxidatively degraded during catalysis.


Metal: Ru
Ligand type: Amino-sulfonamide; Benzene
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Alcohol oxidation
Max TON: 200
ee: ---
PDB: ---
Notes: ---

Metal: Ru
Ligand type: Amino-sulfonamide; Benzene
Host protein: Avidin (Av)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Alcohol oxidation
Max TON: 230
ee: ---
PDB: ---
Notes: ---

Metal: Ru
Ligand type: Bipyridine; C6Me6
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Alcohol oxidation
Max TON: 173
ee: ---
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Alcohol oxidation
Max TON: 7.5
ee: ---
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Bipyridine; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Alcohol oxidation
Max TON: 30
ee: ---
PDB: ---
Notes: ---

Artificial Hydrogenases Based on Cobaloximes and Heme Oxygenase

Artero, V.

ChemPlusChem 2016, 81, 1083-1089, 10.1002/cplu.201600218

The insertion of cobaloxime catalysts in the heme‐binding pocket of heme oxygenase (HO) yields artificial hydrogenases active for H2 evolution in neutral aqueous solutions. These novel biohybrids have been purified and characterized by using UV/visible and EPR spectroscopy. These analyses revealed the presence of two distinct binding conformations, thereby providing the cobaloxime with hydrophobic and hydrophilic environments, respectively. Quantum chemical/molecular mechanical docking calculations found open and closed conformations of the binding pocket owing to mobile amino acid residues. HO‐based biohybrids incorporating a {Co(dmgH)2} (dmgH2=dimethylglyoxime) catalytic center displayed up to threefold increased turnover numbers with respect to the cobaloxime alone or to analogous sperm whale myoglobin adducts. This study thus provides a strong basis for further improvement of such biohybrids, using well‐designed modifications of the second and outer coordination spheres, through site‐directed mutagenesis of the host protein.


Metal: Co
Ligand type: Oxime
Host protein: Heme oxygenase (HO)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: H2 evolution
Max TON: 15.3
ee: ---
PDB: ---
Notes: ---

Artificial Metalloenzyme for Enantioselective Sulfoxidation Based on Vanadyl-Loaded Streptavidin

Ward, T.R.

J. Am. Chem. Soc. 2008, 130, 8085-8088, 10.1021/ja8017219

Nature’s catalysts are specifically evolved to carry out efficient and selective reactions. Recent developments in biotechnology have allowed the rapid optimization of existing enzymes for enantioselective processes. However, the ex nihilo creation of catalytic activity from a noncatalytic protein scaffold remains very challenging. Herein, we describe the creation of an artificial enzyme upon incorporation of a vanadyl ion into the biotin-binding pocket of streptavidin, a protein devoid of catalytic activity. The resulting artificial metalloenzyme catalyzes the enantioselective oxidation of prochiral sulfides with good enantioselectivities both for dialkyl and alkyl-aryl substrates (up to 93% enantiomeric excess). Electron paragmagnetic resonance spectroscopy, chemical modification, and mutagenesis studies suggest that the vanadyl ion is located within the biotin-binding pocket and interacts only via second coordination sphere contacts with streptavidin.


Metal: V
Ligand type: Water
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Genetic
Reaction: Sulfoxidation
Max TON: 27
ee: 93
PDB: ---
Notes: ---

Artificial Metalloenzymes Based on Biotin-Avidin Technology for the Enantioselective Reduction of Ketones by Transfer Hydrogenation

Ward, T.R.

Proc. Natl. Acad. Sci. U. S. A. 2005, 102, 4683-4687, 10.1073/pnas.0409684102

Most physiological and biotechnological processes rely on molecular recognition between chiral (handed) molecules. Manmade homogeneous catalysts and enzymes offer complementary means for producing enantiopure (single-handed) compounds. As the subtle details that govern chiral discrimination are difficult to predict, improving the performance of such catalysts often relies on trial-and-error procedures. Homogeneous catalysts are optimized by chemical modification of the chiral environment around the metal center. Enzymes can be improved by modification of gene encoding the protein. Incorporation of a biotinylated organometallic catalyst into a host protein (avidin or streptavidin) affords versatile artificial metalloenzymes for the reduction of ketones by transfer hydrogenation. The boric acid·formate mixture was identified as a hydrogen source compatible with these artificial metalloenzymes. A combined chemo-genetic procedure allows us to optimize the activity and selectivity of these hybrid catalysts: up to 94% (R) enantiomeric excess for the reduction of p-methylacetophenone. These artificial metalloenzymes display features reminiscent of both homogeneous catalysts and enzymes.


Metal: Ru
Ligand type: Amino-sulfonamide; P-cymene
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 92
ee: 94
PDB: ---
Notes: ---

Metal: Ru
Ligand type: Amino-sulfonamide; Benzene
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 30
ee: 63
PDB: ---
Notes: ---

Artificial Metalloenzymes Derived from Bovine β-Lactoglobulin for the Asymmetric Transfer Hydrogenation of an Aryl Ketone – Synthesis, Characterization and Catalytic Activity

Salmain, M.

Dalton Trans. 2014, 43, 5482-5489, 10.1039/c3dt53253d

Protein hybrids resulting from the supramolecular anchoring to bovine β-lactoglobulin of fatty acid-derived Rh(iii) diimine complexes catalysed the asymmetric transfer hydrogenation of trifluoroacetophenone with up to 32% ee.


Metal: Rh
Ligand type: Cp*; Poly-pyridine
Host protein: ß-lactoglobulin
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Hydrogenation
Max TON: 14
ee: 32
PDB: ---
Notes: ---

Artificial Metalloenzymes for Asymmetric Allylic Alkylation on the Basis of the Biotin–Avidin Technology

Ward, T.R.

Angew. Chem. Int. Ed. 2008, 47, 701-705, 10.1002/anie.200703159

Palladium in the active site: The incorporation of a biotinylated palladium diphosphine within streptavidin yielded an artificial metalloenzyme for the title reaction (see scheme). Chemogenetic optimization of the catalyst by the introduction of a spacer (red star) between biotin (green triangle) and palladium and saturation mutagenesis at position S112X afforded both R‐ and S‐selective artificial asymmetric allylic alkylases.


Metal: Pd
Ligand type: Phosphine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Allylic alkylation
Max TON: 10
ee: 93
PDB: ---
Notes: ---

Artificial Metalloenzymes for Enantioselective Catalysis Based on Biotin-Avidin

Ward, T.R.

J. Am. Chem. Soc. 2003, 125, 9030-9031, 10.1021/ja035545i

Homogeneous and enzymatic catalysis offer complementary means to generate enantiomerically pure compounds. Incorporation of achiral biotinylated rhodium−diphosphine complexes into (strept)avidin yields artificial metalloenzymes for the hydrogenation of N-protected dehydroamino acids. A chemogenetic optimization procedure allows one to produce (R)-acetamidoalanine with 96% enantioselectivity. These hybrid catalysts display features reminiscent both of enzymatic and of homogeneous systems.


Metal: Rh
Ligand type: Phosphine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Hydrogenation
Max TON: ---
ee: 96
PDB: ---
Notes: ---

Artificial Metalloenzymes for Enantioselective Catalysis: The Phenomenon of Protein Accelerated Catalysis

Ward, T.R.

J. Organomet. Chem. 2004, 689, 4868-4871, 10.1016/j.jorganchem.2004.09.032

We report on the phenomenon of protein-accelerated catalysis in the field of artificial metalloenzymes based on the non-covalent incorporation of biotinylated rhodium–diphosphine complexes in (strept)avidin as host proteins. By incrementally varying the [Rh(COD)(Biot-1)]+ vs. (strept)avidin ratio, we show that the enantiomeric excess of the produced acetamidoalanine decreases slowly. This suggests that the catalyst inside (strept)avidin is more active than the catalyst outside the host protein. Both avidin and streptavidin display protein-accelerated catalysis as the protein embedded catalyst display 12.0- and 3.0-fold acceleration over the background reaction with a catalyst devoid of protein. Thus, these artificial metalloenzymes display an increase both in activity and in selectivity for the reduction of acetamidoacrylic acid.


Metal: Rh
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Hydrogenation
Max TON: ---
ee: 94
PDB: ---
Notes: Reduction of acetamidoacrylic acid. 3.0-fold protein acceleration.

Metal: Rh
Host protein: Avidin (Av)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Hydrogenation
Max TON: ---
ee: 39
PDB: ---
Notes: Reduction of acetamidoacrylic acid. 12.0-fold protein acceleration.

Artificial Metalloenzymes for Olefin Metathesis Based on the Biotin-(Strept)Avidin Technology

Ward, T.R.

Chem. Commun. 2011, 47, 12065, 10.1039/c1cc15004a

Incorporation of a biotinylated Hoveyda-Grubbs catalyst within (strept)avidin affords artificial metalloenzymes for the ring-closing metathesis of N-tosyl diallylamine in aqueous solution. Optimization of the performance can be achieved either by chemical or genetic means.


Metal: Ru
Ligand type: Carbene
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 14
ee: ---
PDB: ---
Notes: RCM

Metal: Ru
Ligand type: Carbene
Host protein: Avidin (Av)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 19
ee: ---
PDB: ---
Notes: RCM

Artificial Metalloenzymes for the Diastereoselective Reduction of NAD+ to NAD2H

Ward, T.R.

Org. Biomol. Chem. 2015, 13, 357-360, 10.1039/c4ob02071e

Stereoselectively labelled isotopomers of NAD(P)H are highly relevant for mechanistic studies of enzymes which utilize them as redox equivalents.


Metal: Ir
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: ---
Max TON: ---
ee: ---
PDB: ---
Notes: ---

Artificial Metalloenzymes: (Strept)avidin as Host for Enantioselective Hydrogenation by Achiral Biotinylated Rhodium-Diphosphine Complexes

Ward, T.R.

J. Am. Chem. Soc. 2004, 126, 14411-14418, 10.1021/ja0476718

We report on the generation of artificial metalloenzymes based on the noncovalent incorporation of biotinylated rhodium−diphosphine complexes in (strept)avidin as host proteins. A chemogenetic optimization procedure allows one to optimize the enantioselectivity for the reduction of acetamidoacrylic acid (up to 96% ee (R) in streptavidin S112G and up to 80% ee (S) in WT avidin). The association constant between a prototypical cationic biotinylated rhodium−diphosphine catalyst precursor and the host proteins was determined at neutral pH:  log Ka = 7.7 for avidin (pI = 10.4) and log Ka = 7.1 for streptavidin (pI = 6.4). It is shown that the optimal operating conditions for the enantioselective reduction are 5 bar at 30 °C with a 1% catalyst loading.


Metal: Rh
Ligand type: Phosphine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Hydrogenation
Max TON: ---
ee: 94
PDB: ---
Notes: ---

Artificial Metalloenzymes with the Neocarzinostatin Scaffold: Toward a Biocatalyst for the Diels–Alder Reaction

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

ChemBioChem 2016, 17, 433-440, 10.1002/cbic.201500445

A new artificial enzyme formed by associating NCS‐3.24 with a copper complex catalyzed the Diels–Alder cyclization of cyclopentadiene with 2‐azachalcone and led to an increase in the formation of the exo‐products. Molecular modeling proposed the preferred relative positioning of both the Trojan horse complex and the two substrates.


Metal: Cu
Ligand type: Phenanthroline
Anchoring strategy: Supramolecular
Optimization: ---
Max TON: 33
ee: ---
PDB: ---
Notes: Up to endo/exo ratio 62:38