Characterization of anthocyanin p-coumaroyltransferase in flowers of Iris ensata

Malvidin and petunidin 3-( p-coumaroyl)rhamnosylglucoside-5-glucosides as well as nonacylated 3-rhamnosylglucoside-5-glucoside of these anthocyanidins were detected as major anthocyanins in cyanic flowers of Iris ensata. Enzyme extracts from flower buds of this plant catalyzed the transfer of the p-coumaroyl moiety from p-coumaroyl-CoA to both the anthocyanidin 3-rhamnosylglucoside and 3-rhamnosylglucoside-5-glucoside to form the anthocyanidin 3-( p-coumaroyl) rhamnosylglucoside and 3-( p-coumaroyl) rhamnosylglucoside-5-glucoside, at a ratio of ca. 1 to 4, respectively. The activities of this enzyme were also examined for various cyanic and acyanic cultivars, in addition to the characterization of the p-coumaroyltransferase. The sequence of acylation and 5-glucosylation in the anthocyanin biosynthesis of this plant is discussed.