Bioanorganische Chemie (Ward)

Merging organometallic chemistry with biotechnology

Artificial metalloenzymes

Organometallic- and enzymatic catalysis have evolved independently over the past four decades. In many respects, these approaches can be viewed as complementary. By incorporating an organometallic moiety within a protein host, we create artificial metallo-enzymes, with properties reminiscent both of homogeneous and enzymatic catalysis. The main focus of our research is to exploit such hybrid systems towards various applications.

• Enantioselective catalysis (white biotechnology)
• Synthetic biology (metabolic engineering)
• Bio-nanotechnology

In order to ensure unambiguous localisation of the organometallic moiety within the host protein, we rely on various anchoring strategies.

• Covalent anchoring exploiting carbonic anhydrase as scaffold
• Supramolecular anchoring exploiting the biotin-streptavidin couple
• Dative anchoring upon repurposing proteins with latent facial triad motifs

Basic concept

In the spirit of E. Fischer's Lock and Key. The anchor (red; for example biotin) displays a very high affinity for the host protein (brown; for example streptavidin (Ka 1014 M–1)). A catalytically competent organometallic moiety (green), linked via a spacer (blue) to biotin is combined with streptavidin to yield an artificial metalloenzyme. A broadly applicable chemogenetic optimization strategy relies on

i) mutations (*) on streptavidin and

ii) variation of the spacer and the bidentate ligand

This strategy can be applied to any host protein-cofactor couple.

The chemogenetic optimisation strategy combines random mutagenesis (the rows) of the host protein with chemical variation of the anchored cofactor (the columns). After screening various spacers and ligands, a directed evolution protocol allows to screen thousands of mutants with the selected cofactor to identify versatile artificial metalloenzyme.

A Mosaic of applications

Reactions Implemented

• Hydrogenation
• Transfer hydrogenation
• Ketones, enones, imines, NAD(P)+
• Allylic substitution
• C-H activation
• Suzuki cross-coupling
• Metathesis
• Alcohol oxidation
• Sulfoxidation
• Dihydroxylation
• Peroxidation
• Michael addition
• Enzyme cascades
• DNA recognition

Current

• In vivo catalysis
• Directed evolution
• Alternative metabolism
• Cross-regulation
• Off-equilibrium thermodynamics
• Catalytic drugs
• Biofuels
• Multi-electron processes
• Artificial photosynthesis