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University of Basel

29 August 2016

Bringing artificial enzymes closer to nature

Scientists at the University of Basel, ETH Zurich in Basel, and NCCR Molecular Systems Engineering have developed an artificial metalloenzyme that catalyses a reaction inside of cells without equivalent in nature. This could be a prime example for creating new non-natural metabolic pathways inside living cells, as reported today in Nature.

The artificial metalloenzyme, termed biot-Ru–SAV, was created using the biotinstreptavidin technology. This method relies on the high affinity of the protein streptavidin for the vitamin biotin, where compounds bound to biotin can be introduced into the protein to generate artificial enzymes. In this study the authors introduced an organometallic compound, with the metal ruthenium at its base. Organometallic compounds are molecules containing at least one bond between a metal and a carbon atom, and are often used as catalysts in industrial chemical reactions. However, organometallic catalysts perform poorly, if at all, in aqueous solutions or cellular-like environments, and need to be incorporated into protein scaffolds like streptavidin to overcome these limitations.

Representation of the new-to-nature olefin metathesis reaction in E. coli using a ruthenium-based artificial metalloenzyme to produce novel high added-value chemicals. (Image: NCCR Molecular Systems Engineering)
Representation of the new-to-nature olefin metathesis reaction in E. coli using a ruthenium-based artificial metalloenzyme to produce novel high added-value chemicals. (Image: NCCR Molecular Systems Engineering)

“The goal was to create an artificial metalloenzyme that can catalyse olefin metathesis, a reaction mechanism that is not present among natural enzymes,” says Thomas R Ward, Professor at the Department of Chemistry, University of Basel, and senior author of the study. The olefin metathesis reaction is a method for the formation and redistribution of carbon-carbon double bonds widely used in laboratory research and large-scale industrial productions of various chemical products. Biot-Ru–SAV catalyses a ring-closing metathesis to produce a fluorescent molecule for easy detection and quantification.

Periplasm as reaction compartment

However, the environment inside a living cell is far from ideal for the proper functioning of organometallic-based enzymes. “The main breakthrough was the idea to use the periplasm of Escherichia coli as a reaction compartment, whose environment is much better suited for an olefin metathesis catalyst,” says Markus Jeschek, a researcher from the team of co-supervising author Sven Panke at the Department of Biosystems Science and Engineering, ETH Zurich in Basel. The periplasm, the space between the inner cytoplasmic membrane and the bacterial outer membrane in gram-negative bacteria, contains low concentrations of metalloenzymes inhibitors, such as glutathione.

NCCR Molecular Systems Engineering

Molecular Systems Engineering is a National Centre of Competence in Research (NCCR) funded by the Swiss National Science Foundation (SNSF), and headed by the University of Basel and ETH Zürich. This particular NCCR combines the disciplines chemistry, biology, physics with bioinformatic and engineering. The scientific aim is to synthesise, assemble and engineer molecular modules into molecular factories approaching the complexity of a cell. These molecular factories will be used for industrial production, or to control cellular systems in health and disease.

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