Biocatalytic Synthesis of Phenyl Benzoate Esters Using the Amide Ligase ClxA

Abstract

The synthesis of ester bonds using lipases is one of the most frequently performed reactions in biocatalysis, yet examples of the enzymatic synthesis of phenyl benzoate esters are comparatively rare. In this report we show that the ligase ClxA, from Clostridium cavendishii, initially reported to have roles in amide bond formation in the biosynthesis of benzoxazole antibiotics, is an effective catalyst for the formation of phenyl benzoate esters from acid and phenol substrates using ATP in an aqueous medium. The structure of ClxA was determined by X-ray crystallography in complex with both AMP and 3,4aminohydroxybenzoic acid, and used as a platform to engineer the enzyme to create variants N226L and K140A possessing broader substrate specificity for ester formation, and also the ability to synthesise native amide product oligomers.