Biosynthesis of Epipyrone A Reveals a Highly Specific Membrane-Bound Fungal C -Glycosyltransferase for Pyrone Galactosylation.

Epipyrone A is a unique C -galactosylated 4-hydroxy-2-pyrone derivative with an antifungal potential from the fungus Epicoccum nigrum . We elucidated its biosynthesis via heterologous expression and characterized an unprecedented membrane-bound pyrone C -glycosyltransferase biochemically. Molecular docking and mutagenesis experiments suggested a possible mechanism for the heterocyclic C -glycosylation and the importance of a transmembrane helix for its catalysis. These results expand the repertoire of C -glycosyltransferases and provide new insights into the formation of C -glycosides in fungi.