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Insights into E. coli cyclopropane fatty acid synthase (CFAS) towards enantioselective carbene free biocatalytic cyclopropanation.

Iman Omar, Michele Crotti, Chuhan Li, Krisztina Pisak, Blazej Czemerys, Salvatore Ferla Orcid Logo, Aster van Noord, Caroline Paul, Kersti Karu, Cagakan Ozbalci, Ulrike Eggert, Richard Lloyd, Sarah Barry, Daniele Castagnolo

Angewandte Chemie International Edition

Swansea University Author: Salvatore Ferla Orcid Logo

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DOI (Published version): 10.1002/anie.202403493

Abstract

Cyclopropane fatty acid synthases (CFAS) are a class of S-adenosylmethionine (SAM) dependent methyltransferase enzymes able to catalyse the cyclopropanation of unsaturated phospholipids. Since CFAS enzymes employ SAM as a methylene source to cyclopropanate alkene substrates, they have the potential...

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Published in: Angewandte Chemie International Edition
ISSN: 1433-7851 1521-3773
Published: Wiley
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URI: https://cronfa.swan.ac.uk/Record/cronfa66386
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Abstract: Cyclopropane fatty acid synthases (CFAS) are a class of S-adenosylmethionine (SAM) dependent methyltransferase enzymes able to catalyse the cyclopropanation of unsaturated phospholipids. Since CFAS enzymes employ SAM as a methylene source to cyclopropanate alkene substrates, they have the potential to be mild and more sustainable biocatalysts for cyclopropanation transformations than current carbene based approaches. This work describes the characterisation of E. coli CFAS enzyme (ecCFAS) and its exploitation in the stereoselective biocatalytic synthesis of cyclopropyl lipids. ecCFAS was found to convert phosphatidylglycerol (PG) to methyl dihydrosterculate 1 from in up to 58% conversion and 73% ee and the absolute configuration (9S,10R) was established. Substrate tolerance of ecCFAS was found to be correlated with the electronic properties of phospholipid headgroups and for the first time ecCFAS was found to catalyse cyclopropanation of both phospholipid chains to form dicyclopropanated products. In addition, mutagenesis and in-silico experiments were carried out to identify the enzyme residues with key roles in catalysis and to provide structural insights into the lipid substrate preference of ecCFAS. Finally, the biocatalytic synthesis of methyl dihydrosterculate 1 and its deuterated analogue was also accomplished combining pure ecCFAS with the SAM regenerating AtHMT enzyme in presence of CH3I and CD3I.
College: Faculty of Medicine, Health and Life Sciences
Funders: BBSRC LIDo BBSRC-BIOCATNET