Biocatalysis takes advantage of the remarkable properties of enzymes to perform chemical reactions with high efficiency and selectivity. It is a valuable tool for the synthesis of complex molecules, particularly when the selective production of a single enantiomer is required, a major challenge in
fine chemistry* and pharmaceutical development. To expand the range of accessible chemical transformations, researchers are developing artificial metalloenzymes that combine the selective properties of proteins with the reactivity of inorganic catalysts.
In this study, researchers from
CEA-Irig/LCBM have taken a new original step in the design of artificial metalloenzymes by directly constructing an inorganic active site within protein crystals. After stabilization of
cross-linked enzyme crystals* of
NikA* (CLEC), a
manganese-based Salen complex* (Mn(Salen)) was covalently anchored onto an amino acid, a cysteine residue specifically introduced into the protein. This strategy enables the selection of a new organized protein environment for the active site, thereby allowing it to catalyze an enantioselective epoxidation reaction.
Thanks to this newly created artificial active site, the resulting metalloenzyme catalyzes the epoxidation of
cis-β-methylstyrene* with high enantioselectivity, reaching up to 90% enantiomeric excess. These results demonstrate that CLEC can serve as an effective platform for designing
biohybrid catalysts* that combine the properties of a protein with those of an inorganic complex. Their use as
heterogeneous catalysts* also enables the recovery and reuse of these biocatalysts.
© CEA-Irig/LCBM/BioCE
Figure: System stabilisation, formation of the catalytic site, and the catalytic reaction – all directly within a crystal.
This study highlights the potential of cross-linked enzyme crystals as a platform for designing new artificial metalloenzymes. By enabling the direct construction of an artificial active site within a stabilized protein matrix, this approach combines the selectivity of an enzyme with the reactivity of an inorganic catalyst, while providing the advantages of a recoverable and reusable heterogeneous catalyst.
Artificial metalloenzyme*: Hybrid catalyst combining a protein and a metal complex. This approach aims to create new catalytic functions by combining the selectivity of enzymes with the reactivity of metal catalysts.
Epoxidation*: Addition of an oxygen atom to a double bond between two carbon atoms in unsaturated hydrocarbons, forming a three-atom ring called an epoxide.
Enantioselectivity*: The ability of a catalyst to preferentially promote the formation of one of the two three-dimensional forms (enantiomers) of the same molecule. This selectivity is essential when the two enantiomers have different biological properties.
Fine chemistry*: Field of chemistry that designs and manufactures complex, pure, high-value-added molecules, typically produced in small or medium quantities. These molecules are intended for various sectors, including pharmaceuticals, agrochemicals, cosmetics, electronics, and perfumery. The focus is on mastering synthesis processes, quality, purity, and reproducibility. Pharmaceutical chemistry is one example.
Cross-Linked Enzyme Crystals (CLEC)*: Enzyme crystals stabilized by chemical bonds between protein molecules. This approach preserves the protein’s structure while improving its stability and facilitating its use as a recoverable and reusable catalyst.
NikA*: A protein found in the bacterium Escherichia coli capable of transporting nickel ions (Ni2+) across the membrane.
Salen-type manganese complex*: Inorganic complex containing a manganese ion held at the center of a molecular clamp by a Salen-type ligand.
Cis-β-methylstyrene*: Aromatic alkene derived from styrene, used as a model to evaluate the catalyst’s efficiency and selectivity.
Biohybrid catalyst*: A catalyst that combines biologically derived components, such as proteins or enzymes, with synthetic components, such as metal complexes, to create new catalytic properties.
Heterogeneous catalysis*: Catalytic process in which the catalyst is in a different phase from the reactants—for example, in solid form in a liquid reaction medium. This approach facilitates the recovery and reuse of the catalyst.
UMR :
LCBM - UGA, CNRS, CEA, UMR 5249.
Fundings : Agence Nationale de la Recherche (ANR-18-CE07-0034-2 PRC NI(k)AGARA) (France), LabEx ARCANE program (ANR-11-LABX-0003-01) (France), Graduate School on Chemistry, Biology and Health of Univ Grenoble Alpes CBH-EUR-GS (ANR-17-EURE-0003) (France).