1 Preparation of Artificial Metalloenzymes

Springer eBooks, 2020

In between traditional homogeneous metal catalysts and enzyme catalysts, a new class of hybrid catalysts named artificial metalloenzymes resulting from the controlled embedding of transition metal species (ions, synthetic inorganic or organometallic complexes) within natural, geneticallyengineered or even de novode novo protein scaffolds currently undergoes a tremendous development at the academic level. This family of hybrid assemblies ideally combines the features of their individual components, allowing a wide range of chemical reactions, including new-to-nature reactions, to be catalyzed under mild, eco-compatible conditions with high chemo-and/or stereoselectivity. This chapter intends to summarize the most remarkable achievements in artificial metalloenzyme design and properties

Johnson Matthey Technology Review, 2020

, before moving to the University of Cambridge to begin a PhD on the synthesis and reactivity of Lewis acidic, heterobimetallic main group compounds. Shortly after obtaining her PhD in 2005, she was appointed to a joint College Lectureship in the

Applied Organometallic Chemistry, 2005

Homogeneous and enzymatic catalysis offer complementary means to generate enantiomerically pure compounds. For this reason, in a biomimetic spirit, efforts are currently under way in different groups to design artificial enzymes. Two complementary strategies are possible to incorporate active organometallic catalyst precursors into a protein environment. The first strategy utilizes covalent anchoring of the organometallic complexes into the protein environment. The second strategy relies on the use of non-covalent incorporation of the organometallic precursor into the protein. In this review, attention is focused on the use of semisynthetic enzymes to produce efficient enantioselective hybrid catalysts for a given reaction. This article also includes our recent research results and implications in developing the biotin-avidin technology to localize the biotinylated organometallic catalyst precursor within a well-defined protein environment.

Israel Journal of Chemistry, 2014

ChemBioChem, 2006

. Artificial metalloenzymes for enantioselective catalysis based on the incorporation of a catalytically active metal fragment within a host protein. The interaction between the metal fragment and the host protein may variously be supramolecular, dative, or covalent in nature.

2016

Studies and development of artificial metalloenzymes have developed into vibrant areas of research. It is expected that artificial metalloenzymes will be able to combine the best of enzymatic and homogenous catalysis, that is, a broad catalytic scope, high selectivity and activity under mild, aqueous conditions. Artificial metalloenzyme consist of a host protein and a newly introduced artificial metal center. The host protein merely functions as ligand controlling selectivity and augmenting reactivity, while the metal center determines the reactivity. Potential applications range from catalytic production of fine chemicals and feedstock to electron transfer utilization (e.g. fuel cells, water splitting) and medical research (e.g. metabolic screening). Particularly modern asymmetric synthesis is expected to benefit from a successful combination of the power of biocatalysis (substrate conversion via multi-step or cascade reactions, potentially immortal catalyst, unparalleled selectivity and optimization by evolutionary methods) with the versatility and mechanism based optimization methods of homogeneous catalysis. However, so far systems are either limited in structural diversity (biotin-avidin technology) or fail to deliver the selectivities expected (covalent approaches). This thesis explores a novel strategy based on the site-selective incorporation of unnatural, metal binding amino acids into a host protein. The unnatural amino acids can either serve directly as metal binding centers can be used as anchoring points for artificial metallo-cofactors. The identification expression, purification and modification of a suitable protein scaffolds

Nature, 2016

The field of biocatalysis has advanced from harnessing natural enzymes to using directed evolution to obtain new biocatalysts with tailor-made functions. Several tools have recently been developed to expand the natural enzymatic repertoire with abiotic reactions. For example, artificial metalloenzymes, which combine the versatile reaction scope of transition metals with the beneficial catalytic features of enzymes, offer an attractive means to engineer new reactions. Three complementary strategies exist: repurposing natural metalloenzymes for abiotic transformations; in silico metalloenzyme (re-)design; and incorporation of abiotic cofactors into proteins. The third strategy offers the opportunity to design a wide variety of artificial metalloenzymes for non-natural reactions. However, many metal cofactors are inhibited by cellular components and therefore require purification of the scaffold protein. This limits the throughput of genetic optimization schemes applied to artificial m...

HAL (Le Centre pour la Communication Scientifique Directe), 2020

Our recent research is turning towards the elaboration of artificial metalloenzymes that catalyze reactions of interest for organic chemistry under eco-compatible conditions. First, totally artificial metalloenzymes that catalyze selective oxidations in water are described following three main lines: (i) Insertion of microperoxidase 8 into Metal Organic Frameworks leading to new artificial metalloenzymes that catalyze the selective oxidation of dyes and sulfides by H2O2 ; (ii) Design of a new polyimine polymer-based artificial reductase allowing the reductive activation of dioxygen and its use as an oxygen atom source for selective oxidations catalyzed by metal complexes including metalloporphyrins, copper complexes or Polyoxometallates and, (iii) Design of new artificial metalloenzymes that catalyze in the presence of photoactivable ruthenium complexes the photoreduction of H2O and the concommitant oxidation of sulfides. Second, the synthesis of new artificial metalloenzymes that catalyze the stereoselective Diels-Alder reaction is described following three strategies: (i) Covalent insertion of metal complexes into a new family of thermostable artificial proteins based on alpha-helical repeated motifs (αReps), (ii) Substitution of the native Fe ion of a cupin-like protein, ACCO oxidase, by a copper(II) ion and (iii) Insertion of a copper(II) complex-antagonist conjugate into an adenosine receptor at the surface of living HEK cells.

Chemical Society Reviews, 2005

Enantioselective catalysis is one of the most efficient ways to synthesize high-added-value enantiomerically pure organic compounds. As the subtle details which govern enantioselection cannot be reliably predicted or computed, catalysis relies more and more on a combinatorial approach. Biocatalysis offers an attractive, and often complementary, alternative for the synthesis of enantiopure products. From a combinatorial perspective, the potential of directed evolution techniques in optimizing an enzyme's selectivity is unrivaled. In this review, attention is focused on the construction of artificial metalloenzymes for enantioselective catalytic applications. Such systems are shown to combine properties of both homogeneous and enzymatic kingdoms. This review also includes our recent research results and implications in the development of new semisynthetic metalloproteins for the enantioselective hydrogenation of N-protected dehydroamino acids.

2020

Bioinorganic chemists tackled the challenge to unravel the mechanisms that allow the protein matrix to modulate the catalytic activity of metal-containing cofactors through the development of artificial systems. In this perspective, heme-proteins represent a significant source of inspiration: researchers have attempted for decades to develop efficient and selective metalloporphyrin-based catalysts. Significant advance has been achieved in the design and engineering of protein scaffolds to host metalloporphyrins and to modulate their reactivity. Peptidebased architectures of different sizes have been exploited for the construction of catalytic systems. Among them, synthetic porphyrin-peptide conjugates known as "Mimochromes" represent an important class of artificial heme enzymes. Their structure consists of two α-helical peptides covalently linked to a metalloporphyrin core, resulting into a helix-heme-helix sandwich. Their simple scaffold has been optimized to reproduce the functional properties of peroxidases. Mimochrome VI*a (MC6*a), in its Fe III complex, recently emerged as the best artificial peroxidase known so far, overcoming the catalytic efficiency of horseradish peroxidase (HRP) in ABTS oxidation. Moreover, the cobalt derivative (Co-MC6*a) behaves as a very promising catalyst in hydrogen evolution reactions. These recent achievements prompted us to further evaluate the versatility of the MC6*a scaffold towards metal replacement, by swapping iron to manganese. The primary aim of this PhD project was to expand the scope of transformations accessible by MC6*a complexes in oxidation chemistry. Taking into account the catalytic promiscuity of iron and manganese porphyrins towards diverse oxidative transformations, the analysis of the spectroscopic, redox and catalytic properties of Fe-and Mn-MC6*a has been performed. 2 Compared to other peptide-porphyrin conjugates with a fully solvent-exposed distal site, both Fe-and Mn-MC6*a display an increased ability to promote the deprotonation of metal-bound water and hydrogen peroxide. This property allows MC6*a complexes to reach their highest activity towards H2O2 at lower pH values, approaching those of the natural counterparts. Both Fe-and Mn-MC6*a demonstrated to be efficient and robust catalysts in the H2O2-mediated sulfoxidation of thioethers, being among the most active artificial heme enzymes studied for this reaction. The two catalysts displayed divergent behaviours towards the oxidation of indole. Notably, Mn-MC6*a displays higher chemo-selectivity compared to Fe-MC6*a, but also surpasses most of hemeenzymes examined to the same end. Mn-MC6*a represents one of the most proficient catalysts for indole oxidation, mainly due to the possibility of controlling the formation of different oxidation products with high selectivity. Among them, the formation and isolation of the highly reactive 3-oxindolenine is very important, because it could represent a useful synthon in organic synthesis. Overall, the results of this PhD thesis pave the way for the application of mimochromes to synthetic chemistry. These catalysts fill the middle ground between small-molecule and biological catalysts, since they own a minimal structure that enables substrate promiscuity and a designed peptide scaffold that modulates the reactivity of the metal ion.