50 publications

50 publications

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: ---

A Highly Active Biohybrid Catalyst for Olefin Metathesis in Water: Impact of a Hydrophobic Cavity in a β-Barrel Protein

Okuda, J.

ACS Catal. 2015, 5, 7519-7522, 10.1021/acscatal.5b01792

A series of Grubbs–Hoveyda type catalyst precursors for olefin metathesis containing a maleimide moiety in the backbone of the NHC ligand was covalently incorporated in the cavity of the β-barrel protein nitrobindin. By using two protein mutants with different cavity sizes and choosing the suitable spacer length, an artificial metalloenzyme for olefin metathesis reactions in water in the absence of any organic cosolvents was obtained. High efficiencies reaching TON > 9000 in the ROMP of a water-soluble 7-oxanorbornene derivative and TON > 100 in ring-closing metathesis (RCM) of 4,4-bis(hydroxymethyl)-1,6-heptadiene in water under relatively mild conditions (pH 6, T = 25–40 °C) were observed.


Metal: Ru
Ligand type: Carbene
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 9900
ee: ---
PDB: ---
Notes: ROMP (cis/trans: 48/52)

Metal: Ru
Ligand type: Carbene
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 100
ee: ---
PDB: ---
Notes: RCM

A Hybrid Ring- Opening Metathesis Polymerization Catalyst Based on an Engineered Variant of the Beta-Barrel Protein FhuA

Okuda, J.; Schwaneberg, U.

Chem. - Eur. J. 2013, 19, 13865-13871, 10.1002/chem.201301515

A β‐barrel protein hybrid catalyst was prepared by covalently anchoring a Grubbs–Hoveyda type olefin metathesis catalyst at a single accessible cysteine amino acid in the barrel interior of a variant of β‐barrel transmembrane protein ferric hydroxamate uptake protein component A (FhuA). Activity of this hybrid catalyst type was demonstrated by ring‐opening metathesis polymerization of a 7‐oxanorbornene derivative in aqueous solution.


Metal: Ru
Ligand type: Carbene
Host protein: FhuA ΔCVFtev
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 955
ee: ---
PDB: ---
Notes: ROMP

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: ---

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: ---

Aqueous Phase Transfer Hydrogenation of Aryl Ketones Catalysed by Achiral Ruthenium(II) and Rhodium(III) Complexes and their Papain Conjugates

Salmain, M.

Appl. Organomet. Chem. 2013, 27, 6-12, 10.1002/aoc.2929

Several ruthenium and rhodium complexes including 2,2′‐dipyridylamine ligands substituted at the central N atom by an alkyl chain terminated by a maleimide functional group were tested along with a newly synthesized Rh(III) complex of unsubstituted 2,2′‐dipyridylamine as catalysts in the transfer hydrogenation of aryl ketones in neat water with formate as hydrogen donor. All of them except one led to the secondary alcohol products with conversion rates depending on the metal complex. Site‐specific anchoring of the N‐maleimide complexes to the single free cysteine residue of the cysteine endoproteinase papain endowed this protein with transfer hydrogenase properties towards 2,2,2‐trifluoroacetophenone. Quantitative conversions were reached with the Rh‐based biocatalysts, while modest enantioselectivities were obtained in certain reactional conditions.


Metal: Rh
Ligand type: Cp*; Poly-pyridine
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Hydrogenation
Max TON: 96
ee: 15
PDB: ---
Notes: ---

Artificial Diels–Alderase based on the Transmembrane Protein FhuA

Okuda, J.

Beilstein J. Org. Chem. 2016, 12, 1314-1321, 10.3762/bjoc.12.124

Copper(I) and copper(II) complexes were covalently linked to an engineered variant of the transmembrane protein Ferric hydroxamate uptake protein component A (FhuA ΔCVFtev). Copper(I) was incorporated using an N-heterocyclic carbene (NHC) ligand equipped with a maleimide group on the side arm at the imidazole nitrogen. Copper(II) was attached by coordination to a terpyridyl ligand. The spacer length was varied in the back of the ligand framework. These biohybrid catalysts were shown to be active in the Diels–Alder reaction of a chalcone derivative with cyclopentadiene to preferentially give the endo product.


Metal: Cu
Ligand type: Terpyridine
Host protein: FhuA
Anchoring strategy: Cystein-maleimide
Optimization: Chemical
Max TON: ---
ee: ---
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 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

A Structural View of Synthetic Cofactor Integration into [FeFe]-Hydrogenases

Apfel, U.-P.; Happe, T.; Kurisu, G.

Chem. Sci. 2016, 7, 959-968, 10.1039/C5SC03397G

Crystal structures of semisynthetic [FeFe]-hydrogenases with variations in the [2Fe] cluster show little structural differences despite strong effects on activity.


Metal: Fe
Ligand type: CN; CO; Dithiolate
Anchoring strategy: Dative
Optimization: Chemical
Reaction: H2 evolution
Max TON: ---
ee: ---
PDB: 4XDC
Notes: H2 evolution activity of the ArM: 2874 (mmol H2)*min-1*(mg protein)-1.

Asymmetric Catalytic Sulfoxidation by a Novel VIV8 Cluster Catalyst in the Presence of Serum Albumin: A Simple and Green Oxidation System

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.


Metal: V
Anchoring strategy: Undefined
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: 140
ee: 77
PDB: ---
Notes: Screening with different serum albumins.

Biocompatibility and Therapeutic Potential of Glycosylated Albumin Artificial Metalloenzymes

Tanaka, K.

Nat. Catal. 2019, 2, 780-792, 10.1038/s41929-019-0317-4

The ability of natural metalloproteins to prevent inactivation of their metal cofactors by biological metabolites, such as glutathione, is an area that has been largely ignored in the field of artificial metalloenzyme (ArM) development. Yet, for ArM research to transition into future therapeutic applications, biocompatibility remains a crucial component. The work presented here shows the creation of a human serum albumin-based ArM that can robustly protect the catalytic activity of a bound ruthenium metal, even in the presence of 20 mM glutathione under in vitro conditions. To exploit this biocompatibility, the concept of glycosylated artificial metalloenzymes (GArM) was developed, which is based on functionalizing ArMs with N-glycan targeting moieties. As a potential drug therapy, this study shows that ruthenium-bound GArM complexes could preferentially accumulate to varying cancer cell lines via glycan-based targeting for prodrug activation of the anticancer agent umbelliprenin using ring-closing metathesis.


Metal: Ru
Ligand type: Hoveyda–Grubbs
Anchoring strategy: Supramolecular
Optimization: Chemical
Max TON: 29.9
ee: ---
PDB: ---
Notes: ---

Bovine Serum Albumin-Cobalt(II) Schiff Base Complex Hybrid: An Efficient Artificial Metalloenzyme for Enantioselective Sulfoxidation using Hydrogen Peroxide

Bian, H.-D.; Liang, H.

Dalton Trans. 2016, 45, 8061-8072, 10.1039/C5DT04507J

An artificial metalloenzyme (BSA–CoL) based on the incorporation of a cobalt(ii) Schiff base complex {CoL, H2L = 2,2′-[(1,2-ethanediyl)bis(nitrilopropylidyne)]bisphenol} with bovine serum albumin (BSA) has been synthesized and characterized.


Metal: Co
Ligand type: Amine; Phenolate
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: 98
ee: 87
PDB: ---
Notes: ---

Catalytic Water Oxidation by Iridium-Modified Carbonic Anhydrase

Lee, S.-Y.

Chem. - Asian J. 2018, 13, 334-341, 10.1002/asia.201701543

Carbonic anhydrase (CA) is a ubiquitous metalloenzyme with a Zn cofactor coordinated to trigonal histidine imidazole moieties in a tetrahedral geometry. Removal of the Zn cofactor in CA and subsequent binding of Ir afforded CA[Ir]. Under mild and neutral conditions (30 °C, pH 7), CA[Ir] exhibited water‐oxidizing activity with a turnover frequency (TOF) of 39.8 min−1, which is comparable to those of other Ir‐based molecular catalysts. Coordination of Ir to the apoprotein of CA is thermodynamically preferred and is associated with an exothermic energy change (ΔH) of −10.8 kcal mol−1, which implies that the CA apoprotein is stabilized by Ir binding. The catalytic oxygen‐evolving activity of CA[Ir] is displayed only if Ir is bound to CA, which functions as an effective biological scaffold that activates the Ir center for catalysis. The results of this study indicate that the histidine imidazoles at the CA active site could be exploited as beneficial biological ligands to provide unforeseen biochemical activity by coordination to a variety of transition‐metal ions.


Metal: Ir
Ligand type: Amino acid
Anchoring strategy: Metal substitution
Optimization: Chemical
Reaction: Water oxidation
Max TON: ---
ee: ---
PDB: ---
Notes: Sodium periodate as sacrificial oxidant. TOF at pH 7 and 30°C is 39.8 min-1.

Chalcogenide Substitution in the [2Fe] Cluster of [FeFe]-Hydrogenases Conserves High Enzymatic Activity

Apfel, U.-P.; Happe, T.

Dalton Trans. 2017, 46, 16947-16958, 10.1039/C7DT03785F

Combination of biological and chemical methods allow for creation of [FeFe]-hydrogenases with an artificial synthetic cofactor.


Metal: Fe
Ligand type: CN; CO; Diselenolate
Anchoring strategy: Dative
Optimization: Chemical
Reaction: H2 evolution
Max TON: ---
ee: ---
PDB: 5OEF
Notes: ---

Chemically Engineered Papain as Artificial Formate Dehydrogenase for NAD(P)H Regeneration

Salmain, M.

Org. Biomol. Chem. 2011, 9, 5720, 10.1039/c1ob05482a

Organometallic complexes of the general formula [(η6-arene)Ru(N⁁N)Cl]+ and [(η5-Cp*)Rh(N⁁N)Cl]+ where N⁁N is a 2,2′-dipyridylamine (DPA) derivative carrying a thiol-targeted maleimide group, 2,2′-bispyridyl (bpy), 1,10-phenanthroline (phen) or ethylenediamine (en) and arene is benzene, 2-chloro-N-[2-(phenyl)ethyl]acetamide or p-cymene were identified as catalysts for the stereoselective reduction of the enzyme cofactors NAD(P)+ into NAD(P)H with formate as a hydride donor. A thorough comparison of their effectiveness towards NAD+ (expressed as TOF) revealed that the RhIII complexes were much more potent catalysts than the RuII complexes. Within the RuII complex series, both the N⁁N and arene ligands forming the coordination sphere had a noticeable influence on the activity of the complexes. Covalent anchoring of the maleimide-functionalized RuII and RhIII complexes to the cysteine endoproteinase papain yielded hybrid metalloproteins, some of them displaying formate dehydrogenase activity with potentially interesting kinetic parameters.


Metal: Rh
Ligand type: Cp*; Poly-pyridine
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Hydrogenation
Max TON: ---
ee: ---
PDB: ---
Notes: TOF = 52.1 h-1 for NAD+

Chemical Optimization of Artificial Metalloenzymes Based on the Biotin-Avidin Technology: (S)-Selective and Solvent-Tolerant Hydrogenation Catalysts via the Introduction of Chiral Amino Acid Spacers

Ward, T.R.

Chem. Commun. 2005, 4815, 10.1039/b509015f

Incorporation of biotinylated-[rhodium(diphosphine)]+ complexes, with enantiopure amino acid spacers, in streptavidin affords solvent-tolerant and selective artificial metalloenzymes: up to 91% ee (S) in the hydrogenation of N-protected dehydroamino acids.


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

Cobaloxime-Based Artificial Hydrogenase

Artero, V.

Inorg. Chem. 2014, 53, 8071-8082, 10.1021/ic501014c

Cobaloximes are popular H2 evolution molecular catalysts but have so far mainly been studied in nonaqueous conditions. We show here that they are also valuable for the design of artificial hydrogenases for application in neutral aqueous solutions and report on the preparation of two well-defined biohybrid species via the binding of two cobaloxime moieties, {Co(dmgH)2} and {Co(dmgBF2)2} (dmgH2 = dimethylglyoxime), to apo Sperm-whale myoglobin (SwMb). All spectroscopic data confirm that the cobaloxime moieties are inserted within the binding pocket of the SwMb protein and are coordinated to a histidine residue in the axial position of the cobalt complex, resulting in thermodynamically stable complexes. Quantum chemical/molecular mechanical docking calculations indicated a coordination preference for His93 over the other histidine residue (His64) present in the vicinity. Interestingly, the redox activity of the cobalt centers is retained in both biohybrids, which provides them with the catalytic activity for H2 evolution in near-neutral aqueous conditions.


Metal: Co
Ligand type: Oxime
Host protein: Myoglobin (Mb)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: H2 evolution
Max TON: 5
ee: ---
PDB: ---
Notes: Sperm whale myoglobin

Copper–Phthalocyanine Conjugates of Serum Albumins as Enantioselective Catalysts in Diels–Alder Reactions

Reetz, M.T.

Angew. Chem. Int. Ed. 2006, 45, 2416-2419, 10.1002/anie.200504561

Chirality from blood: Serum albumins form strong complexes with CuII–phthalocyanines, leading to protein conjugates. These hybrid catalysts promote enantioselective Diels–Alder reactions, such as that of azachalcones 1 with cyclopentadiene (2) to give products 3 with 85–98 % ee.


Metal: Cu
Ligand type: Phthalocyanine
Anchoring strategy: Supramolecular
Optimization: Chemical
Max TON: 45.5
ee: 98
PDB: ---
Notes: Chirality from blood: Serum albumins form strong complexes with CuII–phthalocyanines, leading to protein conjugates. These hybrid catalysts promote enantioselective Diels–Alder reactions, such as that of azachalcones 1 with cyclopentadiene (2) to give products 3 with 85–98 % ee.

Covalent Anchoring of a Racemization Catalyst to CALB-Beads: Towards Dual Immobilization of DKR Catalysts

Klein Gebbink, R.J.M.; van Koten, G.

Tetrahedron Lett. 2011, 52, 1601-1604, 10.1016/j.tetlet.2011.01.106

The preparation of a heterogeneous bifunctional catalytic system, combining the catalytic properties of an organometallic catalyst (racemization) with those of an enzyme (enantioselective acylation) is described. A novel ruthenium phosphonate inhibitor was synthesized and covalently anchored to a lipase immobilized on a solid support (CALB, Novozym® 435). The immobilized bifunctional catalytic system showed activity in both racemization of (S)-1-phenylethanol and selective acylation of 1-phenylethanol.


Metal: Ru
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Acylation
Max TON: ---
ee: >99%
PDB: ---
Notes: Lipase CALB is immobilized on a solid support (Novozym®435). Dynamic kinetic resolution (DKR) of 1-phenylethanol to the acylated product.

Cross-Linked Artificial Enzyme Crystals as Heterogeneous Catalysts for Oxidation Reactions

Cavazza, C.; Ménage, S.

J. Am. Chem. Soc. 2017, 139, 17994-18002, 10.1021/jacs.7b09343

Designing systems that merge the advantages of heterogeneous catalysis, enzymology, and molecular catalysis represents the next major goal for sustainable chemistry. Cross-linked enzyme crystals display most of these essential assets (well-designed mesoporous support, protein selectivity, and molecular recognition of substrates). Nevertheless, a lack of reaction diversity, particularly in the field of oxidation, remains a constraint for their increased use in the field. Here, thanks to the design of cross-linked artificial nonheme iron oxygenase crystals, we filled this gap by developing biobased heterogeneous catalysts capable of oxidizing carbon–carbon double bonds. First, reductive O2 activation induces selective oxidative cleavage, revealing the indestructible character of the solid catalyst (at least 30 000 turnover numbers without any loss of activity). Second, the use of 2-electron oxidants allows selective and high-efficiency hydroxychlorination with thousands of turnover numbers. This new technology by far outperforms catalysis using the inorganic complexes alone, or even the artificial enzymes in solution. The combination of easy catalyst synthesis, the improvement of “omic” technologies, and automation of protein crystallization makes this strategy a real opportunity for the future of (bio)catalysis.


Metal: Fe
Ligand type: ---
Host protein: NikA
Anchoring strategy: Supramolecular
Optimization: Chemical
Max TON: 28000
ee: ---
PDB: 5ON0
Notes: Cross-Linked Enzyme Crystals (CLEC) as catalysts.

Metal: Fe
Ligand type: ---
Host protein: NikA
Anchoring strategy: Supramolecular
Optimization: Chemical
Max TON: 5900
ee: ---
PDB: 5ON0
Notes: Cross-Linked Enzyme Crystals (CLEC) as catalysts.

Design of Metal Cofactors Activated by a Protein–Protein Electron Transfer System

Watanabe, Y.

Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 9416-9421, 10.1073/pnas.0510968103

Protein-to-protein electron transfer (ET) is a critical process in biological chemistry for which fundamental understanding is expected to provide a wealth of applications in biotechnology. Investigations of protein–protein ET systems in reductive activation of artificial cofactors introduced into proteins remains particularly challenging because of the complexity of interactions between the cofactor and the system contributing to ET. In this work, we construct an artificial protein–protein ET system, using heme oxygenase (HO), which is known to catalyze the conversion of heme to biliverdin. HO uses electrons provided from NADPH/cytochrome P450 reductase (CPR) through protein–protein complex formation during the enzymatic reaction. We report that a FeIII(Schiff-base), in the place of the active-site heme prosthetic group of HO, can be reduced by NADPH/CPR. The crystal structure of the Fe(10-CH2CH2COOH-Schiff-base)·HO composite indicates the presence of a hydrogen bond between the propionic acid carboxyl group and Arg-177 of HO. Furthermore, the ET rate from NADPH/CPR to the composite is 3.5-fold faster than that of Fe(Schiff-base)·HO, although the redox potential of Fe(10-CH2CH2COOH-Schiff-base)·HO (−79 mV vs. NHE) is lower than that of Fe(Schiff-base)·HO (+15 mV vs. NHE), where NHE is normal hydrogen electrode. This work describes a synthetic metal complex activated by means of a protein–protein ET system, which has not previously been reported. Moreover, the result suggests the importance of the hydrogen bond for the ET reaction of HO. Our Fe(Schiff-base)·HO composite model system may provide insights with regard to design of ET biosystems for sensors, catalysts, and electronics devices.


Metal: Fe
Ligand type: Salophen
Host protein: Heme oxygenase (HO)
Anchoring strategy: Reconstitution
Optimization: Chemical
Reaction: O2 reduction
Max TON: ---
ee: ---
PDB: 1WZD
Notes: ---

Diruthenium Diacetate-Catalyzed Aerobic Oxidation of Hydroxylamines and Improved Chemoselectivity by Immobilization to Lysozyme

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.


Metal: Ru
Ligand type: Amino acid; OAc
Host protein: Lysozyme
Anchoring strategy: Dative
Optimization: Chemical
Max TON: 1000
ee: ---
PDB: ---
Notes: ---

Enantioselective Transfer Hydrogenation of Ketone Catalysed by Artificial Metalloenzymes Derived from Bovine β-Lactoglobulin

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.


Metal: Rh
Ligand type: Cp*; Poly-pyridine
Host protein: ß-lactoglobulin
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Hydrogenation
Max TON: 34
ee: 26
PDB: ---
Notes: ---

Highly Efficient Cyclic Dinucleotide Based Artificial Metalloribozymes for Enantioselective Friedel–Crafts Reactions in Water

Chen, Y.; Wang, C.

Angew. Chem. Int. Ed. 2020, 59, 3444-3449, 10.1002/anie.201912962

The diverse secondary structures of nucleic acids are emerging as attractive chiral scaffolds to construct artificial metalloenzymes (ArMs) for enantioselective catalysis. DNA‐based ArMs containing duplex and G‐quadruplex scaffolds have been widely investigated, yet RNA‐based ArMs are scarce. Here we report that a cyclic dinucleotide of c‐di‐AMP and Cu2+ ions assemble into an artificial metalloribozyme (c‐di‐AMP⋅Cu2+) that enables catalysis of enantioselective Friedel–Crafts reactions in aqueous media with high reactivity and excellent enantioselectivity of up to 97 % ee. The assembly of c‐di‐AMP⋅Cu2+ gives rise to a 20‐fold rate acceleration compared to Cu2+ ions. Based on various biophysical techniques and density function theory (DFT) calculations, a fine coordination structure of c‐di‐AMP⋅Cu2+ metalloribozyme is suggested in which two c‐di‐AMP form a dimer scaffold and the Cu2+ ion is located in the center of an adenine‐adenine plane through binding to two N7 nitrogen atoms and one phosphate oxygen atom.


Metal: Cu
Ligand type: RNA
Host protein: RNA
Anchoring strategy: Dative
Optimization: Chemical
Max TON: 20
ee: 97
PDB: ---
Notes: ---

Hybrid [FeFe]-Hydrogenases with Modified Active Sites Show Remarkable Residual Enzymatic Activity

Lubitz, W.; Reijerse, E.

Biochemistry 2015, 54, 1474-1483, 10.1021/bi501391d

[FeFe]-hydrogenases are to date the only enzymes for which it has been demonstrated that the native inorganic binuclear cofactor of the active site Fe2(adt)(CO)3(CN)2 (adt = azadithiolate = [S-CH2-NH-CH2-S]2–) can be synthesized on the laboratory bench and subsequently inserted into the unmaturated enzyme to yield fully functional holo-enzyme (Berggren, G. et al. (2013) Nature 499, 66–70; Esselborn, J. et al. (2013) Nat. Chem. Biol. 9, 607–610). In the current study, we exploit this procedure to introduce non-native cofactors into the enzyme. Mimics of the binuclear subcluster with a modified bridging dithiolate ligand (thiodithiolate, N-methylazadithiolate, dimethyl-azadithiolate) and three variants containing only one CN– ligand were inserted into the active site of the enzyme. We investigated the activity of these variants for hydrogen oxidation as well as proton reduction and their structural accommodation within the active site was analyzed using Fourier transform infrared spectroscopy. Interestingly, the monocyanide variant with the azadithiolate bridge showed ∼50% of the native enzyme activity. This would suggest that the CN– ligands are not essential for catalytic activity, but rather serve to anchor the binuclear subsite inside the protein pocket through hydrogen bonding. The inserted artificial cofactors with a propanedithiolate and an N-methylazadithiolate bridge as well as their monocyanide variants also showed residual activity. However, these activities were less than 1% of the native enzyme. Our findings indicate that even small changes in the dithiolate bridge of the binuclear subsite lead to a rather strong decrease of the catalytic activity. We conclude that both the Brønsted base function and the conformational flexibility of the native azadithiolate amine moiety are essential for the high catalytic activity of the native enzyme.


Metal: Fe
Ligand type: CN; CO; Dithiolate
Anchoring strategy: Dative
Optimization: Chemical
Max TON: ---
ee: ---
PDB: ---
Notes: H2 evolution: TOF = 450 s-1. H2 oxidation: TOF = 150 s-1.

Hybrid Ruthenium ROMP Catalysts Based on an Engineered Variant of β-Barrel Protein FhuA ΔCVFtev: Effect of Spacer Length

Okuda, J.

Chem. - Asian J. 2015, 10, 177-182, 10.1002/asia.201403005

A biohybrid ring‐opening olefin metathesis polymerization catalyst based on the reengineered β‐barrel protein FhuA ΔCVFtev was chemically modified with respect to the covalently anchored Grubbs–Hoveyda type catalyst. Shortening of the spacer (1,3‐propanediyl to methylene) between the N‐heterocyclic carbene ligand and the cysteine site 545 increased the ROMP activity toward a water‐soluble 7‐oxanorbornene derivative. The cis/trans ratio of the double bond in the polymer was influenced by the hybrid catalyst.


Metal: Ru
Ligand type: Carbene
Host protein: FhuA ΔCVFtev
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 555
ee: ---
PDB: ---
Notes: ROMP; cis/trans = 58/42

Immobilization of Two Organometallic Complexes into a Single Cage to Construct Protein-Based Microcompartment

Ueno, T.

Chem. Commun. 2016, 52, 5463-5466, 10.1039/C6CC00679E

Natural protein-based microcompartments containing multiple enzymes promote cascade reactions within cells. We use the apo-ferritin protein cage to mimic such biocompartments by immobilizing two organometallic Ir and Pd complexes into the single protein cage. Precise locations of the metals and their accumulation mechanism were studied by X-ray crystallography.


Metal: Ir
Ligand type: Amino acid; Cp*
Host protein: Apo-ferritin
Anchoring strategy: Dative
Optimization: Chemical
Reaction: Hydrogenation
Max TON: ~2
ee: 15
PDB: 5E2D
Notes: Tandem reaction (Hydrogenation and Suzuki-Miyaura coupling) to form biphenylethanol from 4-iodoacetophenone and phenylboronic acid. TON and ee are given for the tandem reaction product.

Metal: Pd
Ligand type: Allyl; Amino acid
Host protein: Apo-ferritin
Anchoring strategy: Dative
Optimization: Chemical
Max TON: ~1
ee: 15
PDB: 5E2D
Notes: Tandem reaction (Hydrogenation and Suzuki-Miyaura coupling) to form biphenylethanol from 4-iodoacetophenone and phenylboronic acid.

Manganese Terpyridine Artificial Metalloenzymes for Benzylic Oxygenation and Olefin 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.


Metal: Mn
Ligand type: Poly-pyridine
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Max TON: 19.2
ee: ---
PDB: 3EMM
Notes: ---

Metal: Mn
Ligand type: Poly-pyridine
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Epoxidation
Max TON: 19.8
ee: ---
PDB: 3EMM
Notes: ---