αRep A3: A Versatile Artificial Scaffold for Metalloenzyme Design (original) (raw)

Artificial metalloenzymes: proteins as hosts for enantioselective catalysis

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.

Design of artificial metalloenzymes

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.

From Unnatural Amino Acid Incorporation to Artificial Metalloenzymes

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

Metal-Conjugated Affinity Labels: A New Concept to Create Enantioselective Artificial Metalloenzymes

ChemistryOpen, 2013

Dedicated to Professor Wolfgang A. Herrmann on the occasion of his 65 th birthday Incorporation of artificial metal centers into proteins and peptides has emerged as an important tool in chemical and biological research. Current applications include pharmaceuticals, probes for molecular imaging [3] and contrast agents, [4] tools for biophysical studies targeting metalloprotein functions, metal-directed protein assembly, electrochemical biosensors, and altered electrochemical potential of electron transporting proteins, [8] as well as the synthesis of functional metalloenzymes with non-natural catalytic activity. [9] Particularly artificial metalloenzymes received great interest, since they hold the promise to greatly expand the range of reactions accessible by biocatalysis. A variety of methods to generate artificial metal sites were developed including domain-based directed evolution strategies, [10] engineering of transition-metal binding sites through introduction of coordinating amino acids at geometrically appropriate positions or site-directed in vivo incorporation of artificial metal-chelating amino acids. [12] However, the site-directed anchoring of artificial cofactors representing appropriate ligands or metal complexes has so far been the most successful strategy to achieve good catalytic activities and enantioselectivities. Inspired by the pioneering work of Wilson and Whitesides, Ward revealed the potential of the supramolecular biotin-(strept)avidin technology, which in combination with directed or rationally guided evolution can deliver highly enantioselective organometallic enzyme hybrid (OMEH) catalysts. [15] Such biotin-(strept)avidin-metal conjugates were subsequently tested in a variety of catalytic transformations. [16] In contrast to this supramolecular approach, covalent anchoring of artificial cofactors on proteins can utilize a variety of protein hosts and hence is not limited by the stability range of the biotin-(strept)avidin complex. Originally introduced by Kaiser, covalent attachment of artificial cofactors has been applied to convert proteases, [19] lipases [20] or other non-metal proteins [21] into organometallic enzyme hybrids. However, none of the covalent approaches could so far achieve the enantioselectivities reached by biotin-(strept)avidin conjugates. [9d, 21e] Although metals are introduced site-specifically, most systems generated through a covalent approach possess a flexible linker and hence lack a well-defined localization of the metal center on the surface of the host protein, which is a prerequisite to achieve chiral induction.

Artificial Metalloenzymes for Enantioselective Catalysis: Recent Advances

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.

Directed evolution of artificial metalloenzymes for in vivo metathesis

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...

Current Applications of Artificial Metalloenzymes and Future Developments

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

Artificial Metalloproteins: At the Interface between Biology and Chemistry

JACS Au

Artificial metalloproteins (ArMs) have recently gained significant interest due to their potential to address issues in a broad scope of applications, including biocatalysis, biotechnology, protein assembly, and model chemistry. ArMs are assembled by the incorporation of a non-native metallocofactor into a protein scaffold. This can be achieved by a number of methods that apply tools of chemical biology, computational de novo design, and synthetic chemistry. In this Perspective, we highlight select systems in the hope of demonstrating the breadth of ArM design strategies and applications and emphasize how these systems address problems that are otherwise difficult to do so with strictly biochemical or synthetic approaches.