Biosynthesis of bitter acids in hops

Abstract
The biosynthesis of humulone, an antibacterial bitter acid from hops, was studied by isotope‐incorporation experiments using 13C‐labelled glucose or 2H2O. 13C enrichments, 2H enrichments and 13C13C coupling patterns identify isovaleryl‐CoA, malonyl‐CoA and dimethylallyl pyrophosphate as precursors for humulone. Dimethylallyl pyrophosphate, which serves as a building block for the bitter acid, is generated via the deoxyxylulose pathway of terpenoid biosynthesis. The data confirm that a symmetrical intermediate is involved in humulone formation.