The cyclopropane ring is an important structural motif present in many pharmaceutical compounds and widely used as reactive building blocks in the synthesis of chemicals. Many synthetic strategies to access cyclopropanes have been developed to date, most of which typically require the use of potentially explosive diazo-carbene compounds as substrates. Even recently proposed enzymatic transformations, exploiting cytochromes P450 and myoglobin, require the use of stoichiometric carbene co-substrates, thus narrowing their industrial applications. The CycloproBio project aims to explore cyclopropane synthase (CS) enzymes as a potentially mild method for biocatalytic cyclopropanation. Cyclopropane synthases are SAM dependent transferase enzymes able to catalyse cyclopropanation of unsaturated phospholipids in bacterial membranes. Even if CS are common to most bacteria, many questions on factors affecting their substrate selectivity remain unanswered. Moreover, despite their potential, CS enzymes have not been explored yet as potential biocatalysts. This project will initially characterize the cyclopropane fatty acid synthase (CFAS) from E. coli which has been cloned, expressed and purified in preliminary work. The catalytic properties of the E. coli CFAS will be studied through the development of an appropriate activity assay, the investigation of its substrate specificity and the study of its physio-chemical properties. To broaden the study, genome mining for other CS enzymes from different bacterial species will be carried out to gain insight into the factors which affect the selectivity of these enzymes. Finally, new CS enzyme variants will be generated through rational mutagenesis of putative substrate binding residues. The data generated will provide fundamental information on the CS family. The primary aim of this project is to use this data to develop cyclopropanation biocatalysts for the sustainable synthesis of chemicals and pharmaceuticals.
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