PTases employed in plant natural product biosynthesis. (a) Aromatic PTases (aPTases) catalyze the addition of a terpenoid-derived prenyl group onto an electron-rich aromatic phenolic core, as exemplified by the prenylation of naringenin to form 6-prenylnaringenin and 8-prenylnaringenin. Notably, aPTases often exhibit relaxed substrate specificity and/or relaxed regiospecificity as shown here. As reported, when isolated from hops, the amounts of 6-prenylnaringenin and 8-prenylnaringenin are approximately equal. However, this ratio may not hold true in other plants, which may vary from plant to plant. Additionally, the ratios of each prenylated compound account for 1–2% of total prenylflavonoids in hops and vary dependent on growth conditions making accurate quantification difficult. (b)
cis-PTases catalyze the formation of Z-terpenoids, thus increasing the structural diversity and potential beneficial activity of the broad family of plant terpenoids.