In-vitro prenylation of aromatic intermediates in the biosynthesis of bitter acids in humulus lupulus

Bitter acids are accumulated in the glandular hairs of hop cones. The first step of the biosynthesis of the bitter acids, namely formation of the aromatic intermediates, is catalysed by a chalcone synthase-like enzyme. In the present paper two sequential prenylation steps, leading to first the production of compounds X (4-prenylphlorisovalerophenone) or co-X (4-prenylphlorisobutyrophenone) and thereafter to the production of deoxyhumulone or deoxycohumulone, respectively, are described. An HPLC assay for these prenylation reactions has been set up, and enzyme activities were measured in protein extracts from hop flowerbuds, flowers and young cones. Furthermore, preliminary characterization experiments of the prenyltransferases were performed.