Ustethylin Biosynthesis Implies Phenethyl Derivative Formation in Aspergillus ustus

A highly oxygenated phenethyl derivative ustethylin A was isolated from Aspergillus ustus. Gene deletion, isotope labeling, and heterologous expression proved that the phenethyl core structure is assembled from malonyl-CoA by a polyketide synthase harboring a methyltransferase domain. Propionate was converted via acetyl-CoA to malonyl-CoA and incorporated into the molecule. Modifications on the core structure by three different oxidoreductases and one O-methyltransferase lead to the final product, ustethylin A.