Purification and characterization of anthocyanin 3-aromatic acyltransferase from Perilla frutescens

Hydroxycinnamoyl-CoA:anthocyanin 3-O-glucoside-6"-O-hydroxycinnamoyltransferase (3AT; EC 2.3.1.-) was identified and highly purified from red leaves of Perilla frutescens, which accumulate cyanidin 3-(6-0-p-coumaroyl-beta-D-glucoside)-5-(6-O-malonyl-P-D-glucosid 3AT was a 50 kDa monomer of protein with a pi of 5.3. It catalyzed the transfer of the p-coumaric and caffeic acids from their CoA esters to the 3-glucosyl moiety of delphinidin, cyanidin ;nd pelargonidin 3-glucoside. Anthocyanidin 3,5-diglucosides were also good substrates, while cyanidin 3-rutinoside was a poor substrate. Malonyl-CoA was not used by the enzyme as an acyl-donor. Aromatic acylation of anthocyanin by 3AT caused a bathochromic shift. Lower K-m values for anthoyanidin 3-glucoside than 3,5-diglucoside may indicate that acylation of cyanidin 3-glucoside precedes 5-O-glucosylation in vivo. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.