Altering the Regiospecificity of a CatecholO‐methyltransferase through Rational Design: Vanilloid vs. Isovanilloid Motifs in the B‐ring of Flavonoids

Abstract

AbstractRational re‐design of the substrate pocket of phenylpropanoid‐flavonoidO‐methyltransferase (PFOMT) fromMesembryanthemum crystallinum, an enzyme that selectively methylates the 3′‐position (=meta‐position) in catechol‐moieties of flavonoids to guiacol‐moieties, provided the basis for the generation of variants with opposite, i. e. 4′‐ (para‐) regioselectivity and enhanced catalytic efficiency. A double variant (Y51R/N202W) identified through a newly developed colorimetric assay efficiently modified thepara‐position in flavanone and flavanonol substrates, providing access to the sweetener molecule hesperetin and other rare plant flavonoids having an isovanilloid motif.