Emergence of a proton exchange-based isomerization and lactonization mechanism in the plant coumarin synthase COSY

Abstract

Plant biosynthetic enzymes rapidly evolve to catalyze specialized reactions. Here, the authors present the crystal structure and mechanism of COSY, the enzyme involved in coumarin biosynthesis of the BAHD-acyltransferase family that catalyzes an intramolecular acyl transfer reaction through a proton exchange mechanism.