24 publications

24 publications

A Clamp-Like Biohybrid Catalyst for DNA Oxidation

Nolte, R.J.M.

Nat. Chem. 2013, 5, 945-951, 10.1038/NCHEM.1752

In processive catalysis, a catalyst binds to a substrate and remains bound as it performs several consecutive reactions, as exemplified by DNA polymerases. Processivity is essential in nature and is often mediated by a clamp-like structure that physically tethers the catalyst to its (polymeric) template. In the case of the bacteriophage T4 replisome, a dedicated clamp protein acts as a processivity mediator by encircling DNA and subsequently recruiting its polymerase. Here we use this DNA-binding protein to construct a biohybrid catalyst. Conjugation of the clamp protein to a chemical catalyst with sequence-specific oxidation behaviour formed a catalytic clamp that can be loaded onto a DNA plasmid. The catalytic activity of the biohybrid catalyst was visualized using a procedure based on an atomic force microscopy method that detects and spatially locates oxidized sites in DNA. Varying the experimental conditions enabled switching between processive and distributive catalysis and influencing the sliding direction of this rotaxane-like catalyst.


Metal: Mn
Ligand type: Porphyrin
Host protein: gp45
Anchoring strategy: Covalent
Optimization: ---
Max TON: ---
ee: ---
PDB: 1CZD
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: ---

A Site-Selective Dual Anchoring Strategy for Artificial Metalloprotein Design

Lu, Y.

J. Am. Chem. Soc. 2004, 126, 10812-10813, 10.1021/ja046908x

Introducing nonnative metal ions or metal-containing prosthetic groups into a protein can dramatically expand the repertoire of its functionalities and thus its range of applications. Particularly challenging is the control of substrate-binding and thus reaction selectivity such as enantioselectivity. To meet this challenge, both non-covalent and single-point attachments of metal complexes have been demonstrated previously. Since the protein template did not evolve to bind artificial metal complexes tightly in a single conformation, efforts to restrict conformational freedom by modifying the metal complexes and/or the protein are required to achieve high enantioselectivity using the above two strategies. Here we report a novel site-selective dual anchoring (two-point covalent attachment) strategy to introduce an achiral manganese salen complex (Mn(salen)), into apo sperm whale myoglobin (Mb) with bioconjugation yield close to 100%. The enantioselective excess increases from 0.3% for non-covalent, to 12.3% for single point, and to 51.3% for dual anchoring attachments. The dual anchoring method has the advantage of restricting the conformational freedom of the metal complex in the protein and can be generally applied to protein incorporation of other metal complexes with minimal structural modification to either the metal complex or the protein.


Metal: Mn
Ligand type: Salen
Host protein: Myoglobin (Mb)
Anchoring strategy: Covalent
Optimization: Genetic
Reaction: Sulfoxidation
Max TON: 3.9
ee: 51
PDB: 1MBO
Notes: Sperm whale myoglobin

Coordinated Design of Cofactor and Active Site Structures in Development of New Protein Catalysts

Watanabe, Y.

J. Am. Chem. Soc. 2005, 127, 6556-6562, 10.1021/ja045995q

New methods for the synthesis of artificial metalloenzymes are important for the construction of novel biocatalysts and biomaterials. Recently, we reported new methodology for the synthesis of artificial metalloenzymes by reconstituting apo-myoglobin with metal complexes (Ohashi, M. et al., Angew Chem., Int. Ed.2003, 42, 1005−1008). However, it has been difficult to improve their reactivity, since their crystal structures were not available. In this article, we report the crystal structures of MIII(Schiff base)·apo-A71GMbs (M = Cr and Mn). The structures suggest that the position of the metal complex in apo-Mb is regulated by (i) noncovalent interaction between the ligand and surrounding peptides and (ii) the ligation of the metal ion to proximal histidine (His93). In addition, it is proposed that specific interactions of Ile107 with 3- and 3‘-substituent groups on the salen ligand control the location of the Schiff base ligand in the active site. On the basis of these results, we have successfully controlled the enantioselectivity in the sulfoxidation of thioanisole by changing the size of substituents at the 3 and 3‘ positions. This is the first example of an enantioselective enzymatic reaction regulated by the design of metal complex in the protein active site.


Metal: Mn
Ligand type: Salophen
Host protein: Myoglobin (Mb)
Anchoring strategy: Reconstitution
Optimization: Chemical & genetic
Max TON: ---
ee: ---
PDB: 1V9Q
Notes: ---

Metal: Cr
Ligand type: Salophen
Host protein: Myoglobin (Mb)
Anchoring strategy: Reconstitution
Optimization: Chemical & genetic
Max TON: ---
ee: ---
PDB: 1J3F
Notes: ---

Metal: Mn
Ligand type: Salen
Host protein: Myoglobin (Mb)
Anchoring strategy: Reconstitution
Optimization: Chemical & genetic
Max TON: ---
ee: ---
PDB: ---
Notes: ---

Metal: Cr
Ligand type: Salen
Host protein: Myoglobin (Mb)
Anchoring strategy: Reconstitution
Optimization: Chemical & genetic
Max TON: ---
ee: ---
PDB: ---
Notes: ---

Covalent Versus Non-covalent (Biocatalytic) Approaches for Enantioselective Sulfoxidation Catalyzed by Corrole Metal Complexes

Gross, Z.

Cat. Sci. Technol. 2011, 1, 578, 10.1039/c1cy00046b

Oxidation of thioanisoles, catalyzed by chiral manganese(III) and iron(III) corroles, provides the corresponding sulfoxides in moderate chemical yields and low enantioselectivities. Biocatalysis by non-chiral albumin-associated manganese(III) corroles proceeds much better and allows for the enantioselective synthesis of the pharmacologically important R-modafinil, in 88% yield and 73% ee.


Metal: Mn
Ligand type: Corrole
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Sulfoxidation
Max TON: 45
ee: 70
PDB: ---
Notes: ---

C(sp3)–H Bond Hydroxylation Catalyzed by Myoglobin Reconstituted with Manganese Porphycene

Hayashi, T

J. Am. Chem. Soc. 2013, 135, 17282-17285, 10.1021/ja409404k

Myoglobin reconstituted with manganese porphycene was prepared in an effort to generate a new biocatalyst and was characterized by spectroscopic techniques. The X-ray crystal structure of the reconstituted protein reveals that the artificial cofactor is located in the intrinsic heme-binding site with weak ligation by His93. Interestingly, the reconstituted protein catalyzes the H2O2-dependent hydroxylation of ethylbenzene to yield 1-phenylethanol as a single product with a turnover number of 13 at 25 °C and pH 8.5. Native myoglobin and other modified myoglobins do not catalyze C–H hydroxylation of alkanes. Isotope effect experiments yield KIE values of 2.4 and 6.1 for ethylbenzene and toluene, respectively. Kinetic data, log kobs versus BDE(C(sp3)–H) for ethylbenzene, toluene, and cyclohexane, indicate a linear relationship with a negative slope. These findings clearly indicate that the reaction occurs via a rate-determining step that involves hydrogen-atom abstraction by a Mn(O) species and a subsequent rebound hydroxylation process which is similar to the reaction mechanism of cytochrome P450.


Metal: Mn
Ligand type: Porphycene
Host protein: Myoglobin (Mb)
Anchoring strategy: Reconstitution
Optimization: ---
Reaction: Hydroxylation
Max TON: ---
ee: ---
PDB: 2WI8
Notes: ---

Incorporation of Biotinylated Manganese-Salen Complexes into Streptavidin: New Artificial Metalloenzymes for Enantioselective Sulfoxidation

Ward, T.R.

J. Organomet. Chem. 2009, 694, 930-936, 10.1016/j.jorganchem.2008.11.023

Incorporation of achiral biotinylated manganese-salen complexes into streptavidin yields artificial metalloenzymes for aqueous sulfoxidation using hydrogen peroxide. Four biotinylated salen ligands were synthesized and their manganese complexes were tested in combination with several streptavidin mutants, yielding moderate conversions (up to 56%) and low enantioselectivities (maximum of 13% ee) for the sulfoxidation of thioanisole.


Metal: Mn
Ligand type: Oxide; Salen
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Sulfoxidation
Max TON: 28
ee: 13
PDB: ---
Notes: ---

Incorporation of Manganese Complexes into Xylanase: New Artificial Metalloenzymes for Enantioselective Epoxidation

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

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

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


Metal: Mn
Ligand type: Porphyrin
Host protein: Xylanase A (XynA)
Anchoring strategy: Supramolecular
Optimization: ---
Reaction: Epoxidation
Max TON: 21
ee: 80
PDB: ---
Notes: ---

Intramolecular C(sp3)-H Amination of Arylsulfonyl Azides with Engineered and Artificial Myoglobin-Based Catalysts

Fasan, R.

Bioorg. Med. Chem. 2014, 22, 5697-5704, 10.1016/j.bmc.2014.05.015

The direct conversion of aliphatic CH bonds into CN bonds provides an attractive approach to the introduction of nitrogen-containing functionalities in organic molecules. Following the recent discovery that cytochrome P450 enzymes can catalyze the cyclization of arylsulfonyl azide compounds via an intramolecular C(sp3)H amination reaction, we have explored here the CH amination reactivity of other hemoproteins. Various heme-containing proteins, and in particular myoglobin and horseradish peroxidase, were found to be capable of catalyzing this transformation. Based on this finding, a series of engineered and artificial myoglobin variants containing active site mutations and non-native Mn- and Co-protoporphyrin IX cofactors, respectively, were prepared to investigate the effect of these structural changes on the catalytic activity and selectivity of these catalysts. Our studies showed that metallo-substituted myoglobins constitute viable CH amination catalysts, revealing a distinctive reactivity trend as compared to synthetic metalloporphyrin counterparts. On the other hand, amino acid substitutions at the level of the heme pocket were found to be beneficial toward improving the stereo- and enantioselectivity of these Mb-catalyzed reactions. Mechanistic studies involving kinetic isotope effect experiments indicate that CH bond cleavage is implicated in the rate-limiting step of myoglobin-catalyzed amination of arylsulfonyl azides. Altogether, these studies indicate that myoglobin constitutes a promising scaffold for the design and development of CH amination catalysts.


Metal: Mn
Ligand type: Amino acid; Porphyrin
Host protein: Myoglobin (Mb)
Anchoring strategy: Metal substitution
Optimization: Chemical & genetic
Reaction: C-H activation
Max TON: 142
ee: ---
PDB: ---
Notes: ---

Manganese-Substituted Carbonic Anhydrase as a New Peroxidase

Kazlauskas, R.J.

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

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


Metal: Mn
Ligand type: Amino acid
Anchoring strategy: Metal substitution
Optimization: Chemical & genetic
Reaction: Epoxidation
Max TON: 22
ee: 67
PDB: ---
Notes: ---

Metal: Mn
Ligand type: Amino acid
Anchoring strategy: Metal substitution
Optimization: Chemical & genetic
Reaction: Epoxidation
Max TON: 9.5
ee: 55
PDB: 4CAC
Notes: PDB ID 4CAC = Structure of Zn containing hCAII

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: ---

Manganese(V) Porphycene Complex Responsible for Inert C–H Bond Hydroxylation in a Myoglobin Matrix

Oohora, K.

J. Am. Chem. Soc. 2017, 139, 18460-18463, 10.1021/jacs.7b11288

A mechanistic study of H2O2-dependent C–H bond hydroxylation by myoglobin reconstituted with a manganese porphycene was carried out. The X-ray crystal structure of the reconstituted protein obtained at 1.5 Å resolution reveals tight incorporation of the complex into the myoglobin matrix at pH 8.5, the optimized pH value for the highest turnover number of hydroxylation of ethylbenzene. The protein generates a spectroscopically detectable two-electron oxidative intermediate in a reaction with peracid, which has a half-life up to 38 s at 10 °C. Electron paramagnetic resonance spectra of the intermediate with perpendicular and parallel modes are silent, indicating formation of a low-spin MnV-oxo species. In addition, the MnV-oxo species is capable of promoting the hydroxylation of sodium 4-ethylbenzenesulfonate under single turnover conditions with an apparent second-order rate constant of 2.0 M–1 s–1 at 25 °C. Furthermore, the higher bond dissociation enthalpy of the substrate decreases the rate constant, in support of the proposal that the H-abstraction is one of the rate-limiting steps. The present engineered myoglobin serves as an artificial metalloenzyme for inert C–H bond activation via a high-valent metal species similar to the species employed by native monooxygenases such as cytochrome P450.


Metal: Mn
Ligand type: Amino acid; Porphycene
Host protein: Myoglobin (Mb)
Anchoring strategy: Reconstitution
Optimization: ---
Reaction: Hydroxylation
Max TON: 13
ee: ---
PDB: 5YL3
Notes: ---

Metal Incorporated Horseradish Peroxidase (HRP) Catalyzed Oxidation of Resveratrol: Selective Dimerization or Decomposition

Pan, Y.

RSC Adv. 2013, 3, 22976, 10.1039/c3ra43784a

Horseradish Peroxidase (HRP) is a commercially available and prevalently used peroxidase with no specific substrate binding domain. However, after being incorporated with different metal cations, new catalytic functions were found in biomimetic oxidation of resveratrol. Based on the results of screening, Ca, Cu, Fe and Mn incorporated enzymes showed distinctive effects, either decomposition or dimerization products were observed.


Metal: Ca; Co; Mn; Ni; Zn
Ligand type: Undefined
Anchoring strategy: Undefined
Optimization: Chemical
Reaction: Oxidation
Max TON: ---
ee: ---
PDB: ---
Notes: Oxidation of resveratrol. Dimerisation product obtained.

Multifunctional Nanoenzymes from Carbonic Anhydrase Skeleton

Yilmaz, F.

Process Biochem. 2018, 72, 71-78, 10.1016/j.procbio.2018.06.005

Carbonic anhydrase (carbonic dehydratase) (CA) is a metalloenzyme that contains zinc (Zn2+) ion in its active site. CA catalyzes the reversible conversion of carbon dioxide and water to bicarbonate and protons. Zn2+ ions, which are present in the active site of the enzyme, interact with the substrate molecules directly and cause catalytic effect. In this study, a nano-enzyme system was designed in aqueous solutions at room temperature and under nitrogen atmosphere to use the CA enzyme without any pre-treatment and deformation in its structure. The novel concept ANADOLUCA (AmiNo Acid (monomer) Decorated and Light Underpinning Conjugation Approach) was used for this process, nano CA enzyme of size 93 nm was synthesized. The activity of the synthesized nano CA was measured following the change in absorbance during the conversion of 4-nitrophenylacetate (NPA) to 4-nitrophenylate ion at 348 nm for a period of 10 min at 25 °C compared with free CA enzyme. Km and Vmax values for nano CA enzyme were found to be 0.442 mM and 1.6 × 10−3 mM min-1, respectively, whereas Km and Vmax values for free CA were found to be 0.471 mM and 1.5 × 10−3 mM min-1, respectively. In addition to these, the Zn2+ ion present in the active site of the nano CA enzyme was replaced by rodium metal. This nanorodium-substituted CA has been investigated as a new reductase enzyme for the stereoselective hydrogenation of olefins. Then, the Zn2+ ion in the active site of the nano CA enzyme was replaced with manganese metal to enhance the enzyme structure, thereby gaining characteristics of peroxidase. This newly synthesized nano manganese-substituted CA enzyme was investigated for its role as a peroxidase, which could be an alternative for hydrogen peroxidases.


Metal: Zn
Ligand type: Amino acid
Host protein: Carbonic anhydrase (CA)
Anchoring strategy: Metal substitution
Optimization: Chemical
Reaction: Hydrolysis
Max TON: ---
ee: ---
PDB: ---
Notes: Cross-linked carbonic anhydrase nano-enzyme particles (93 nm in diameter). Hydrolysis of 4-nitrophenyl acetate.

Metal: Rh
Ligand type: Amino acid
Host protein: Carbonic anhydrase (CA)
Anchoring strategy: Metal substitution
Optimization: Chemical
Reaction: Hydration
Max TON: ---
ee: ---
PDB: ---
Notes: Cross-linked carbonic anhydrase nano-enzyme particles (93 nm in diameter). Hydration of styrene.

Metal: Mn
Ligand type: Amino acid
Host protein: Carbonic anhydrase (CA)
Anchoring strategy: Metal substitution
Optimization: Chemical
Reaction: Oxidation
Max TON: ---
ee: ---
PDB: ---
Notes: Cross-linked carbonic anhydrase nano-enzyme particles (93 nm in diameter). Oxidation of styrene.

Noncovalent Modulation of pH-Dependent Reactivity of a Mn–Salen Cofactor in Myoglobin with Hydrogen Peroxide

Lu, Y.

Chem. - Eur. J. 2009, 15, 7481-7489, 10.1002/chem.200802449

To demonstrate protein modulation of metal‐cofactor reactivity through noncovalent interactions, pH‐dependent sulfoxidation and 2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid) (ABTS) oxidation reactivity of a designed myoglobin (Mb) containing non‐native Mn–salen complex (1) was investigated using H2O2 as the oxidant. Incorporation of 1 inside the Mb resulted in an increase in the turnover numbers through exclusion of water from the metal complex and prevention of Mn–salen dimer formation. Interestingly, the presence of protein in itself is not enough to confer the increase activity as mutation of the distal His64 in Mb to Phe to remove hydrogen‐bonding interactions resulted in no increase in the turnover numbers, while mutation His64 to Arg, another residue with ability to hydrogen‐bond interactions, resulted in an increase in reactivity. These results strongly suggest that the distal ligand His64, through its hydrogen‐bonding interaction, plays important roles in enhancing and fine‐tuning reactivity of the Mn–salen complex. Nonlinear least‐squares fitting of rate versus pH plots demonstrates that 1⋅Mb(H64X) (X=H, R and F) and the control Mn–salen 1 exhibit pKa values varying from pH 6.4 to 8.3, and that the lower pKa of the distal ligand in 1⋅Mb(H64X), the higher the reactivity it achieves. Moreover, in addition to the pKa at high pH, 1⋅Mb displays another pKa at low pH, with pKa of 5.0±0.08. A comparison of the effect of different pH on sulfoxidation and ABTS oxidation indicates that, while the intermediate produced at low pH conditions could only perform sulfoxidation, the intermediate at high pH could oxidize both sulfoxides and ABTS. Such a fine‐control of reactivity through hydrogen‐bonding interactions by the distal ligand to bind, orient and activate H2O2 is very important for designing artificial enzymes with dramatic different and tunable reactivity from catalysts without protein scaffolds.


Metal: Mn
Ligand type: Salen
Host protein: Myoglobin (Mb)
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: Sulfoxidation
Max TON: 4.1
ee: 50
PDB: ---
Notes: Sperm whale myoglobin

Oxidation Catalysis via Visible-Light Water Activation of a [Ru(bpy)3]2+ Chromophore BSA–Metallocorrole Couple

Gross, Z.; Mahy, J.-P.

Dalton Trans. 2016, 45, 706-710, 10.1039/c5dt04158a

Light induced enantioselective oxidation of an organic molecule with water as the oxygen atom source is demonstrated in a system where chirality is induced by a protein, oxygen atom transfer by a manganese corrole, and photocatalysis by ruthenium complexes.


Metal: Mn
Ligand type: Corrole
Anchoring strategy: Supramolecular
Optimization: ---
Reaction: Sulfoxidation
Max TON: 21
ee: 16
PDB: ---
Notes: Water as oxygen source

Oxidation of Organic Molecules in Homogeneous Aqueous Solution Catalyzed by Hybrid Biocatalysts (Based on the Trojan Horse Strategy)

Mahy, J.-P.

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

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


Metal: Fe
Ligand type: Porphyrin
Host protein: Antibody 7A3
Anchoring strategy: Supramolecular
Optimization: ---
Reaction: Sulfoxidation
Max TON: 9
ee: 10
PDB: ---
Notes: ---

Metal: Mn
Ligand type: Porphyrin
Host protein: Antibody 7A3
Anchoring strategy: Supramolecular
Optimization: ---
Reaction: Epoxidation
Max TON: 105
ee: ---
PDB: ---
Notes: Imidazole as co-catalyst

Peroxidation of Pyrogallol by Antibody−Metalloporphyrin Complexes

Harada, A.

Inorg. Chem. 1997, 36, 6099-6102, 10.1021/ic9610849

Antibody 03-1, which was prepared by immunization with meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) conjugate, has been found to bind strongly to Mn(III)−TCPP and Fe(III)−TCPP complexes with dissociation constants of 4.1 × 10-7 and 1.5 × 10-7 M, respectively, although other monoclonal antibodies raised against TCPP did not bind to these TCPP−metal complexes. The complexes of antibody 03-1 with Mn(III)−TCPP and Fe(III)−TCPP were found to catalyze oxidation of pyrogallol selectively. A Lineweaver-Burk plot for the oxidation of pyrogallol by the antibody−Fe−TCPP complex showed Km = 4.0 mM and kcat = 50 min-1. Studies on the effect of the molar ratio of the antibody to metalloporphyrin on the catalytic activity showed that a 1:1 complex was the most effective for the reaction. The effect of salt (NaCl) on the reaction showed that electrostatic interaction between the antibody and the metalloporphyrin was important for the reaction. The antibody−metalloporphyrin complexes are stable enough to show catalytic activity in the presence of an excess amount of H2O2.


Metal: Mn
Ligand type: Porphyrin
Host protein: Antibody 03-1
Anchoring strategy: Antibody
Optimization: ---
Max TON: 200
ee: ---
PDB: ---
Notes: ---

Metal: Fe
Ligand type: Porphyrin
Host protein: Antibody 03-1
Anchoring strategy: Antibody
Optimization: ---
Max TON: 300
ee: ---
PDB: ---
Notes: ---

Protein Scaffold of a Designed Metalloenzyme Enhances the Chemoselectivity in Sulfoxidation of Thioanisole

Lu, Y.

Chem. Commun. 2008, 1665, 10.1039/b718915j

We demonstrate that incorporation of MnSalen into a protein scaffold enhances the chemoselectivity in sulfoxidation of thioanisole and find that both the polarity and hydrogen bonding of the protein scaffold play an important role in tuning the chemoselectivity.


Metal: Mn
Ligand type: Salen
Host protein: Myoglobin (Mb)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Reaction: Sulfoxidation
Max TON: 5.2
ee: 60
PDB: ---
Notes: Sperm whale myoglobin

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 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: ---

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: ---

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: ---

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: ---