418 publications

418 publications

(η6-Arene) Ruthenium(II) Complexes and Metallo-Papain Hybrid as Lewis Acid Catalysts of Diels–Alder Reaction in Water

Salmain, M.

Dalton Trans. 2010, 39, 5605, 10.1039/c001630f

Covalent embedding of a (η6-arene) ruthenium(II) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels–Alder reaction enhanced by two orders of magnitude in water.


Metal: Ru
Ligand type: Benzene; Phenanthroline
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: Chemical
Max TON: 440
ee: ---
PDB: ---
Notes: TOF = 220 h-1

X-Ray Structure and Designed Evolution of an Artificial Transfer Hydrogenase

Ward, T.R.

Angew. Chem. Int. Ed. 2008, 47, 1400-1404, 10.1002/anie.200704865

A structure is worth a thousand words: Guided by the X‐ray structure of an S‐selective artificial transfer hydrogenase, designed evolution was used to optimize the selectivity of hybrid catalysts. Fine‐tuning of the second coordination sphere of the ruthenium center (see picture, orange sphere) by introduction of two point mutations allowed the identification of selective artificial transfer hydrogenases for the reduction of dialkyl ketones.


Metal: Ru
Ligand type: Amino-sulfonamide; Benzene
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 100
ee: 92
PDB: 2QCB
Notes: ---

Metal: Ru
Ligand type: Amino-sulfonamide; P-cymene
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 97
ee: 96
PDB: 2QCB
Notes: ---

Various Strategies for Obtaining Oxidative Artificial Hemoproteins with a Catalytic Oxidative Activity: From "Hemoabzymes" to "Hemozymes"?

Review

Mahy, J.-P.

J. Porphyr. Phthalocyanines 2014, 18, 1063-1092, 10.1142/S1088424614500813

The design of artificial hemoproteins that could lead to new biocatalysts for selective oxidation reactions using clean oxidants such as O 2 or H 2 O 2 under ecocompatible conditions constitutes a really promising challenge for a wide range of industrial applications. In vivo, such reactions are performed by heme-thiolate proteins, cytochromes P450, that catalyze the oxidation of drugs by dioxygen in the presence of electrons delivered from NADPH by cytochrome P450 reductase. Several strategies were used to design new artificial hemoproteins to mimic these enzymes, that associate synthetic metalloporphyrin derivatives to a protein that is supposed to induce a selectivity in the catalyzed reaction. A first generation of artificial hemoproteins or "hemoabzymes" was obtained by the non-covalent association of synthetic hemes such as N-methyl-mesoporphyrin IX, Fe(III) -α3β-tetra-o-carboxyphenylporphyrin or microperoxidase 8 with monoclonal antibodies raised against these cofactors. The obtained antibody-metalloporphyrin complexes displayed a peroxidase activity and some of them catalyzed the regio-selective nitration of phenols by H 2 O 2/ NO 2 and the stereo-selective oxidation of sulphides by H 2 O 2. A second generation of artificial hemoproteins or "hemozymes", was obtained by the non-covalent association of non-relevant proteins with metalloporphyrin derivatives. Several strategies were used, the most successful of which, named "host-guest" strategy involved the non-covalent incorporation of metalloporphyrin derivatives into easily affordable proteins. The artificial hemoproteins obtained were found to be able to perform efficiently the stereoselective oxidation of organic compounds such as sulphides and alkenes by H 2 O 2 and KHSO 5.


Notes: ---

Various Strategies for Obtaining Artificial Hemoproteins: From "Hemoabzymes" to "Hemozymes"

Mahy, J.-P.

Biochimie 2009, 91, 1321-1323, 10.1016/j.biochi.2009.03.002

The design of artificial hemoproteins that could lead to new biocatalysts for selective oxidation reactions of organic compounds presents a huge interest especially in pharmacology, both for a better understanding of the metabolic profile of drugs and for the synthesis of enantiomerically pure molecules that could be involved in the design of drugs. The present results show that the so-called “host-guest strategy” that involves the non-covalent incorporation of anionic water-soluble iron-porphyrins into xylanase A from Streptomyces lividans, a low cost protein, leads to such an artificial hemoprotein that is able to perform the stereoselective oxidation of sulfides.


Metal: Fe
Ligand type: Porphyrin
Host protein: Xylanase A (XynA)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: ---
ee: 36
PDB: ---
Notes: ---

Vanadium-Catalysed Enantioselective Sulfoxidations: Rational Design of Biocatalytic and Biomimetic Systems

Sheldon, R.A.

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

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


Metal: V
Ligand type: Oxide
Host protein: Phytase
Anchoring strategy: Undefined
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: ---
ee: 68
PDB: ---
Notes: ---

Use of the Confined Spaces of Apo-Ferritin and Virus Capsids as Nanoreactors for Catalytic Reactions

Review

Ueno, T.

Curr. Opin. Chem. Biol. 2015, 25, 88-97, 10.1016/j.cbpa.2014.12.026

Self-assembled protein cages providing nanosized internal spaces which are capable of encapsulating metal ions/complexes, enzymes/proteins have great potential for use as catalytic nanoreactors in efforts to mimic confined cellular environments for synthetic applications. Despite many uses in biomineralization, drug delivery, bio-imaging and so on, applications in catalysis are relatively rare. Because of their restricted size, protein cages are excellent candidates for use as vessels to exert control over reaction kinetics and product selectivity. Virus capsids with larger internal spaces can encapsulate multiple enzymes and can mimic natural enzymatic reactions. The apo-ferritin cage is known to accommodate various metal ions/complexes and suitable for organic transformation reactions in an aqueous medium. This review highlights the importance, prospects and recent significant research on catalytic reactions using the apo-ferritin cage and virus capsids.


Notes: ---

Upregulation of an Artificial Zymogen by Proteolysis

Ward, T.R.

Angew. Chem. Int. Ed. 2016, 55, 11587-11590, 10.1002/anie.201605010

Regulation of enzymatic activity is vital to living organisms. Here, we report the development and the genetic optimization of an artificial zymogen requiring the action of a natural protease to upregulate its latent asymmetric transfer hydrogenase activity.


Metal: Ir
Ligand type: Cp*; Tripeptide
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 2000
ee: 73
PDB: ---
Notes: ---

Transforming Carbonic Anhydrase into Epoxide Synthase by Metal Exchange

Soumillion, P.

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

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


Metal: Mn
Ligand type: Amino acid
Anchoring strategy: Metal substitution
Optimization: Chemical & genetic
Reaction: Epoxidation
Max TON: 4.1
ee: 52
PDB: ---
Notes: ---

Metal: Mn
Ligand type: Amino acid
Anchoring strategy: Metal substitution
Optimization: Chemical & genetic
Reaction: Epoxidation
Max TON: 10.3
ee: 40
PDB: ---
Notes: ---

Toward the Computational Design of Artificial Metalloenzymes: From Protein–Ligand Docking to Multiscale Approaches

Review

Maréchal, J.-D.

ACS Catal. 2015, 5, 2469-2480, 10.1021/acscatal.5b00010

The development of artificial enzymes aims at expanding the scope of biocatalysis. Over recent years, artificial metalloenzymes based on the insertion of homogeneous catalysts in biomolecules have received an increasing amount of attention. Rational or pseudorational design of these composites is a challenging task because of the complexity of the identification of efficient complementarities among the cofactor, the substrate, and the biological partner. Molecular modeling represents an interesting alternative to help in this task. However, little attention has been paid to this field so far. In this manuscript, we aim at reviewing our efforts in developing strategies efficient to computationally drive the design of artificial metalloenzymes. From protein–ligand dockings to multiscale approaches, we intend to demonstrate that modeling could be useful at the different steps of the design. This Perspective ultimately aims at providing computational chemists with illustration of the applications of their tools for artificial metalloenzymes and convincing enzyme designers of the capabilities, qualitative and quantitative, of computational methodologies.


Notes: ---

Towards the Directed Evolution of Hybrid Catalysts

Reetz, M.T.

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

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


Metal: Mn
Ligand type: Salen
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: ---
Reaction: Epoxidation
Max TON: ---
ee: < 10
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Dipyridin-2-ylmethane
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: ---
Reaction: Hydrogenation
Max TON: ---
ee: < 10
PDB: ---
Notes: ---

Towards Evolution of Artificial Metalloenzymes - A Protein Engineer’s Perspective

Review

Schwaneberg, U.

Angew. Chem. Int. Ed. 2019, 58, 4454-4464, 10.1002/anie.201811042

Incorporating artificial metal‐cofactors into protein scaffolds results in a new class of catalysts, termed biohybrid catalysts or artificial metalloenzymes. Biohybrid catalysts can be modified chemically at the first coordination sphere of the metal complex, as well as at the second coordination sphere provided by the protein scaffold. Protein‐scaffold reengineering by directed evolution exploits the full power of nature's diversity, but requires validated screening and sophisticated metal cofactor conjugation to evolve biohybrid catalysts. In this Minireview, we summarize the recent efforts in this field to establish high‐throughput screening methods for biohybrid catalysts and we show how non‐chiral catalysts catalyze reactions enantioselectively by highlighting the first successes in this emerging field. Furthermore, we shed light on the potential of this field and challenges that need to be overcome to advance from biohybrid catalysts to true artificial metalloenzymes.


Notes: ---

Towards Antibody-Mediated Metallo-Porphyrin Chemistry

Keinan, E.

Pure Appl. Chem. 1990, 62, 2013-2019, 10.1351/pac199062102013

An attempt was made to mimic cytochrome P-450-like activity using antibodies elicited against metallo-porphyrins. Monoclonal antibodies raised against a water-soluble Sn(1V) porphyrin complex (1) exhibited Specificity for a variety of monomeric metalloporphyrins, as well as for the b-0x0-Fe(III) porphyrin dimer 2. Some antibodies were found to be more selective for the monomer 1 than for the dimer 2, suggesting an "edge-on" recognition of the planar porphyrin molecule. The catalytic activity of the antibody-metalloporphyrin complexes was investigated using the epoxidation of styrene by iodosobenzene as a model reaction. Three biphasic media were studied for this reaction: reverse micelles, microemulsions, and solid catalyst in organic solvent. The most promising results were obtained with solid catalyst (obtained via lyophilization of equimolar amounts of Mn(TCP)Cl and specific antibody) in dry CHzClz at room temperature, as indicated by the high turnover numbers of the catalyst. A difference in the relative activity of the various monoclonal antibodies (MABs) was noted. The anti-1 antibodies displayed ca. 30-60% higher activity compared to a nonrelevant MAB.


Metal: Mn
Ligand type: Porphyrin
Host protein: Antibody
Anchoring strategy: Supramolecular
Optimization: ---
Max TON: 549
ee: ---
PDB: ---
Notes: ---

The Third Generation of Artificial Dye-Decolorizing Peroxidase Rationally Designed in Myoglobin

Lin, Y.-W.

ACS Catal. 2019, 9, 7888-7893, 10.1021/acscatal.9b02226

Approaches to degradation of industrial dyes are desirable, of which bioremediation is more favorable. In addition to the use of native enzymes, rational design of artificial enzymes provides an alternative approach. Meanwhile, few designs can achieve a catalytic activity comparable to that of native enzymes. We have previously designed two generations of artificial dye-decolorizing peroxidases (DyPs) in myoglobin (Mb) by introduction of Tyr43 and Trp138 in the heme pocket; however, the activity is moderate. To improve the activity of the artificial DyP, we herein designed a third generation by introduction of an additional Trp (P88W) to the protein surface, named F43Y/F138W/P88W Mb. The third generation of artificial DyP was shown to exhibit a catalytic efficiency exceeding that of various native DyPs and comparable to that of the most efficient native DyPs. Titration of reactive blue 19 (RB19) and molecular docking studies revealed crucial roles of Trp88 in substrate binding and oxidation, which acts as a catalytic site. This study not only provides clues for heme protein design but also suggests that the artificial DyP has potential applications for bioremediation in the future.


Metal: Fe
Ligand type: Porphyrin
Host protein: Myoglobin (Mb)
Anchoring strategy: Dative
Optimization: Genetic
Reaction: Peroxidation
Max TON: 30
ee: ---
PDB: ---
Notes: 3rd generation based on previous studies

Thermostable Peroxidase-Activity with a Recombinant Antibody L-Chain-Porphyrin Fe(III) Complex

Imanaka, T.

FEBS Lett. 1995, 375, 273-276, 10.1016/0014-5793(95)01224-3

In order to engineer a new type of catalytic antibody, we attempt to use a monoclonal antibody L chain as a host protein for a porphyrin. TCPP (meso‐tetrakis(4‐carboxyphenyl)porphyine) was chemically synthesized and Balb/c mice were immunized using TCPP as a hapten. Two hybridoma cells (03‐1, 13‐1), that produce monoclonal antibody against TCPP, were obtained. Genes for both H and L chains of monoclonal antibodies were cloned, sequenced and overexpressed using E. coli as a host. ELISA and fluorescence quenching method show that the independent antibody L chains from both Mab03‐1 and Mab13‐1 have specific interaction with TCPP. Furthermore, the recombinant antibody L chain from Mab13‐1 exhibits much higher peroxidase activity than TCPP Fe(III) alone. The enzyme activity was detectable with pyrogallol and ABTS (2,2‐azinobis‐3‐ethylbenzthiazolin‐6‐sulfonic acid) but not with catechol. This new catalytic antibody was extremely thermostable. Optimum temperature of the peroxidase reaction by the complex of 13‐1L chain and TCPP Fe(III) was 90°C, while that the TCPP Fe(III) alone was 60°C.


Metal: Fe
Ligand type: Porphyrin
Anchoring strategy: Antibody
Optimization: ---
Reaction: Peroxidation
Max TON: ---
ee: ---
PDB: ---
Notes: ---

The Rational Design of Semisynthetic Peroxidases

Sheldon, R.A.

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

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


Metal: V
Ligand type: Oxide
Host protein: Phytase
Anchoring strategy: Undefined
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: ---
ee: 66
PDB: ---
Notes: Reaction performed in 30% organic co-solvent.

The Protein Environment Drives Selectivity for Sulfide Oxidation by an Artificial Metalloenzyme

Cavazza, C.; Ménage, S.

ChemBioChem 2009, 10, 545-552, 10.1002/cbic.200800595

Magic Mn–salen metallozyme: The design of an original, artificial, inorganic, complex‐protein adduct, has led to a better understanding of the synergistic effects of both partners. The exclusive formation of sulfoxides by the hybrid biocatalyst, as opposed to sulfone in the case of the free inorganic complex, highlights the modulating role of the inorganic‐complex‐binding site in the protein.


Metal: Mn
Ligand type: Salen
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Sulfoxidation
Max TON: 97
ee: ---
PDB: ---
Notes: ---

The Plasticity of Redox Cofactors: From Metalloenzymes to Redox-Active DNA

Review

Happe, T.; Hemschemeier, A.

Nat. Rev. Chem. 2018, 2, 231-243, 10.1038/s41570-018-0029-3

Metal cofactors considerably widen the catalytic space of naturally occurring enzymes whose specific and enantioselective catalytic activity constitutes a blueprint for economically relevant chemical syntheses. To optimize natural enzymes and uncover novel reactivity, we need a detailed understanding of cofactor–protein interactions, which can be challenging to obtain in the case of enzymes with sophisticated cofactors. As a case study, we summarize recent research on the [FeFe]-hydrogenases, which interconvert protons, electrons and dihydrogen at a unique iron-based active site. We can now chemically synthesize the complex cofactor and incorporate it into an apo-protein to afford functional enzymes. By varying both the cofactor and the polypeptide components, we have obtained detailed knowledge on what is required for a metal cluster to process H2. In parallel, the design of artificial proteins and catalytically active nucleic acids are advancing rapidly. In this Perspective, we introduce these fields and outline how chemists and biologists can use this knowledge to develop novel tailored semisynthetic catalysts.


Notes: ---

The Important Role of Covalent Anchor Positions in Tuning Catalytic Properties of a Rationally Designed MnSalen-Containing Metalloenzyme

Lu, Y.; Zhang, J.-L.

ACS Catal. 2011, 1, 1083-1089, 10.1021/cs200258e

Two questions important to the success in metalloenzyme design are how to attach or anchor metal cofactors inside protein scaffolds and in what way such positioning affects enzymatic properties. We have previously reported a dual anchoring method to position a nonnative cofactor, MnSalen (1), inside the heme cavity of apo sperm whale myoglobin (Mb) and showed that the dual anchoring can increase both the activity and enantioselectivity over single anchoring methods, making this artificial enzyme an ideal system to address the above questions. Here, we report systematic investigations of the effect of different covalent attachment or anchoring positions on reactivity and selectivity of sulfoxidation by the MnSalen-containing Mb enzymes. We have found that changing the left anchor from Y103C to T39C has an almost identical effect of increasing rate by 1.8-fold and increasing selectivity by +15% for S, whether the right anchor is L72C or S108C. At the same time, regardless of the identity of the left anchor, changing the right anchor from S108C to L72C increases the rate by 4-fold and selectivity by +66%. The right anchor site was observed to have a greater influence than the left anchor site on the reactivity and selectivity in sulfoxidation of a wide scope of other ortho-, meta- and para-substituted substrates. The 1·Mb(T39C/L72C) showed the highest reactivity (TON up to 2.32 min–1) and selectivity (ee % up to 83%) among the different anchoring positions examined. Molecular dynamic simulations indicate that these changes in reactivity and selectivity may be due to the steric effects of the linker arms inside the protein cavity. These results indicate that small differences in the anchor positions can result in significant changes in reactivity and enantioselectivity, probably through steric interactions with substrates when they enter the substrate-binding pocket, and that the effects of right and left anchor positions are independent and additive in nature. The finding that the anchoring arms can influence both the positioning of the cofactor and steric control of substrate entrance will help design better functional metalloenzymes with predicted catalytic activity and selectivity.


Metal: Mn
Ligand type: Salen
Host protein: Myoglobin (Mb)
Anchoring strategy: Covalent
Optimization: Genetic
Reaction: Sulfoxidation
Max TON: ---
ee: 83
PDB: ---
Notes: Reaction rate: 2.3 min-1

The Importance of Catalytic Promiscuity for Enzyme Design and Evolution

Review

Mayer, C.; Roelfes, G.

Nat. Rev. Chem. 2019, 3, 687-705, 10.1038/s41570-019-0143-x

The ability of one enzyme to catalyse multiple, mechanistically distinct transformations likely played a crucial role in organisms’ abilities to adapt to changing external stimuli in the past and can still be observed in extant enzymes. Given the importance of catalytic promiscuity in nature, enzyme designers have recently begun to create catalytically promiscuous enzymes in order to expand the canon of transformations catalysed by proteins. This article aims to both critically review different strategies for the design of enzymes that display catalytic promiscuity for new-to-nature reactions and highlight the successes of subsequent directed-evolution efforts to fine-tune these novel reactivities. For the former, we put a particular emphasis on the creation, stabilization and repurposing of reaction intermediates, which are key for unlocking new activities in an existing or designed active site. For the directed evolution of the resulting catalysts, we contrast approaches for enzyme design that make use of components found in nature and those that achieve new reactivities by incorporating synthetic components. Following the critical analysis of selected examples that are now available, we close this Review by providing a set of considerations and design principles for enzyme engineers, which will guide the future generation of efficient artificial enzymes for synthetically useful, abiotic transformations.


Notes: ---

The Bovine Serum Albumin-2-Phenylpropane-1,2-diolatodioxoosmium(VI) Complex as an Enantioselective Catalyst for cis-Hydroxylation of Alkenes

Kokubo, T.; Okano, M.

J. Chem. Soc., Chem. Commun. 1983, 0, 769-770, 10.1039/C39830000769

The 1:1 complex between an osmate ester and bovine serum albumin was found to be effective as an enantioselective catalyst in the cis-hydroxylation of alkenes, affording diols in up to 68% e.e. and turnover of the catalyst with t-butyl hydroperoxide.


Metal: Os
Ligand type: Undefined
Anchoring strategy: Undefined
Optimization: ---
Reaction: Dihydroxylation
Max TON: 40
ee: 68
PDB: ---
Notes: ---

The Ascent of Man(Made Oxidoreductases)

Review

Anderson, J.L.R.

Curr. Opin. Struct. Biol. 2018, 51, 149-155, 10.1016/j.sbi.2018.04.008

Though established 40 years ago, the field of de novo protein design has recently come of age, with new designs exhibiting an unprecedented level of sophistication in structure and function. With respect to catalysis, de novo enzymes promise to revolutionise the industrial production of useful chemicals and materials, while providing new biomolecules as plug-and-play components in the metabolic pathways of living cells. To this end, there are now de novo metalloenzymes that are assembled in vivo, including the recently reported C45 maquette, which can catalyse a variety of substrate oxidations with efficiencies rivalling those of closely related natural enzymes. Here we explore the successful design of this de novo enzyme, which was designed to minimise the undesirable complexity of natural proteins using a minimalistic bottom-up approach.


Notes: ---

Tailoring the Active Site of Chemzymes by Using a Chemogenetic-Optimization Procedure: Towards Substrate-Specific Artificial Hydrogenases Based on the Biotin–Avidin Technology

Ward, T.R.

Angew. Chem. Int. Ed. 2005, 44, 7764-7767, 10.1002/anie.200502000

The combination of chemical‐ with genetic‐optimization strategies (i.e. chemogenetic) allows the production of artificial hydrogenases based on the biotin–avidin technology. In the spirit of enzymes, second‐coordination‐sphere interactions between the host protein (streptavidin) and the substrate (an olefin) allow fine‐tuning of the selectivity to produce either R or S hydrogenation products.


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

Systematic Tuning of Heme Redox Potentials and Its Effects on O2 Reduction Rates in a Designed Oxidase in Myoglobin

Lu, Y.

J. Am. Chem. Soc. 2014, 136, 11882-11885, 10.1021/ja5054863

Cytochrome c Oxidase (CcO) is known to catalyze the reduction of O2 to H2O efficiently with a much lower overpotential than most other O2 reduction catalysts. However, methods by which the enzyme fine-tunes the reduction potential (E°) of its active site and the corresponding influence on the O2 reduction activity are not well understood. In this work, we report systematic tuning of the heme E° in a functional model of CcO in myoglobin containing three histidines and one tyrosine in the distal pocket of heme. By removing hydrogen-bonding interactions between Ser92 and the proximal His ligand and a heme propionate, and increasing hydrophobicity of the heme pocket through Ser92Ala mutation, we have increased the heme E° from 95 ± 2 to 123 ± 3 mV. Additionally, replacing the native heme b in the CcO mimic with heme a analogs, diacetyl, monoformyl, and diformyl hemes, that posses electron-withdrawing groups, resulted in higher E° values of 175 ± 5, 210 ± 6, and 320 ± 10 mV, respectively. Furthermore, O2 consumption studies on these CcO mimics revealed a strong enhancement in O2 reduction rates with increasing heme E°. Such methods of tuning the heme E° through a combination of secondary sphere mutations and heme substitutions can be applied to tune E° of other heme proteins, allowing for comprehensive investigations of the relationship between E° and enzymatic activity.


Metal: Cu
Ligand type: Amino acid
Host protein: Myoglobin (Mb)
Anchoring strategy: Dative
Optimization: Chemical & genetic
Max TON: 1600
ee: ---
PDB: 4FWX
Notes: Sperm whale myoglobin

Synthetic Cascades are Enabled by Combining Biocatalysts with Artificial Metalloenzymes

Turner, N.J.; Ward, T.R.

Nat. Chem. 2013, 5, 93-99, 10.1038/NCHEM.1498

Enzymatic catalysis and homogeneous catalysis offer complementary means to address synthetic challenges, both in chemistry and in biology. Despite its attractiveness, the implementation of concurrent cascade reactions that combine an organometallic catalyst with an enzyme has proven challenging because of the mutual inactivation of both catalysts. To address this, we show that incorporation of a d6-piano stool complex within a host protein affords an artificial transfer hydrogenase (ATHase) that is fully compatible with and complementary to natural enzymes, thus enabling efficient concurrent tandem catalysis. To illustrate the generality of the approach, the ATHase was combined with various NADH-, FAD- and haem-dependent enzymes, resulting in orthogonal redox cascades. Up to three enzymes were integrated in the cascade and combined with the ATHase with a view to achieving (i) a double stereoselective amine deracemization, (ii) a horseradish peroxidase-coupled readout of the transfer hydrogenase activity towards its genetic optimization, (iii) the formation of L-pipecolic acid from L-lysine and (iv) regeneration of NADH to promote a monooxygenase-catalysed oxyfunctionalization reaction.


Metal: Ir
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: 100
ee: > 99
PDB: ---
Notes: Cascade

Synthesis of Hybrid Transition-Metalloproteins via Thiol-Selective Covalent Anchoring of Rh-Phosphine and Ru-Phenanthroline Complexes

Kamer, P.C.J.; Laan, W.

Dalton Trans. 2010, 39, 8477, 10.1039/c0dt00239a

The preparation of hybrid transition metalloproteins by thiol-selective incorporation of organometallic rhodium- and ruthenium complexes is described. Phosphine ligands and two rhodium-diphosphine complexes bearing a carboxylic acid group were coupled to the cysteine of PYP R52G, yielding a metalloenzyme active in the rhodium catalyzed hydrogenation of dimethyl itaconate. The successful coupling was shown by 31P NMR spectroscopy and ESI mass spectroscopy. In addition wild-type PYP (PYP WT), PYP R52G and ALBP were successfully modified with a (η6-arene) ruthenium(II) phenanthroline complex via a maleimide linker.


Metal: Rh
Ligand type: COD; Phosphine
Anchoring strategy: Covalent
Optimization: ---
Reaction: Hydrogenation
Max TON: ---
ee: ---
PDB: 2PHY
Notes: ---

Synthesis of a Sequence-Specific DNA-Cleaving Peptide

Dervan, P.B.

Science 1987, 238, 1129-1132, 10.1126/science.3120311

A synthetic 52-residue peptide based on the sequence-specific DNA-binding domain of Hin recombinase (139-190) has been equipped with ethylenediaminetetraacetic acid (EDTA) at the amino terminus. In the presence of Fe(II), this synthetic EDTA-peptide cleaves DNA at Hin recombination sites. The cleavage data reveal that the amino terminus of Hin(139-190) is bound in the minor groove of DNA near the symmetry axis of Hin recombination sites. This work demonstrates the construction of a hybrid peptide combining two functional domains: sequence-specific DNA binding and DNA cleavage.


Metal: Fe
Ligand type: EDTA
Anchoring strategy: Covalent
Optimization: ---
Reaction: DNA cleavage
Max TON: <1
ee: ---
PDB: ---
Notes: Engineered sequence specificity

Synthesis of a New Estradiol–Iron Metalloporphyrin Conjugate Used to Build up a New Hybrid Biocatalyst for Selective Oxidations by the ‘Trojan Horse’ Strategy

Mahy, J.-P.

Tetrahedron Lett. 2008, 49, 1865-1869, 10.1016/j.tetlet.2008.01.022

The synthesis of a new cationic iron metalloporphyrin–estradiol conjugate is reported. After a study of its association with the anti-estradiol antibody 7A3 by UV–visible spectroscopy, the influence of the antibody on the sulfoxidation of thioanisole by H2O2 catalyzed by the iron–metalloporphyrin has been investigated.


Metal: Fe
Ligand type: Porphyrin
Host protein: Antibody 7A3
Anchoring strategy: Supramolecular
Optimization: ---
Reaction: Sulfoxidation
Max TON: 12
ee: 8
PDB: ---
Notes: ---

Synthesis of a Heterogeneous Artificial Metallolipase with Chimeric Catalytic Activity

Filice, M.

Chem. Commun. 2015, 51, 9324-9327, 10.1039/C5CC02450A

A solid-phase strategy using lipase as a biomolecular scaffold to produce a large amount of Cu2+-metalloenzyme is proposed here. The application of this protocol on different 3D cavities of the enzyme allows creating a heterogeneous artificial metallolipase showing chimeric catalytic activity. The artificial catalyst was assessed in Diels–Alder cycloaddition reactions and cascade reactions showing excellent catalytic properties.


Metal: Cu
Ligand type: Phenanthroline
Anchoring strategy: Covalent
Optimization: Genetic
Max TON: 411
ee: 92
PDB: ---
Notes: ArM is immobilized on Sepabeads. Endo/exo = 93.5%

Metal: Cu
Ligand type: Phenanthroline
Anchoring strategy: Covalent
Optimization: Genetic
Reaction: Reduction
Max TON: ---
ee: ---
PDB: ---
Notes: Cascade reaction: Ester hydrolysis (natural function of the host protein) followed by reduction (function of the designed ArM).

Supramolecular Interactions Between Functional Metal Complexes and Proteins

Review

Duhme-Klair, A.K.

Dalton Trans. 2009, 10141, 10.1039/b915776j

This perspective illustrates the principles and applications of molecular recognition directed binding of transition metal complexes to proteins. After a brief introduction into non-covalent interactions and the importance of complementarity, the focus of the first part is on biological systems that rely on non-covalent forces for metal complex binding, such as proteins involved in bacterial iron uptake and the oxygen-storage protein myoglobin. The second part of the perspective will illustrate how the replacement of native with non-native metal-centres can give rise to artificial metalloenzymes with novel catalytic properties. Subsequently, examples of spectroscopic probes that exploit the characteristic photophysical properties of metal-complexes for the non-covalent labelling, visualisation and investigation of proteins will be described. Finally, the use of kinetically inert metal complexes as scaffolds in drug design will be discussed and it will be highlighted how the binding of metal ions or organometallic fragments to existing drugs or drug candidates can improve their activity or even alter their mode of action.


Notes: ---

Supramolecular Enzyme Mimics

Review

Okamoto, Y.; Ward, T.R.

Comprehensive Supramolecular Chemistry II 2017, 459-510, 10.1016/B978-0-12-409547-2.12551-X

Artificial metalloenzymes result from the incorporation of an organometallic moiety within a macromolecule. In this article, we review the field of artificial metalloenzymes. These are classified according to the host that accommodates the organometallic cofactor: cyclodextrins (“Cyclodextrin-Based Artificial Enzymes” section), ligands bearing a substrate recognition motif (“Artificial Enzymes With Ligands Bearing Substrate Recognition Motifs” section), supramolecular cages (“Cage Molecules as Artificial Enzymes” section), nucleic acids (“DNA-Based Artificial Metalloenzymes” section), and proteins (“Protein-Based Artificial Enzymes” section). Both dative and supramolecular anchoring strategies are reviewed.


Notes: Book chapter