Anthocyanin acyltransferases in cell cultures of Ajuga reptans

Two separable anthocyanin acyltransferases were identified in cell cultures of Ajuga reptans which accumulate acylated cyanidin and delphinidin-based anthocyanins. One catalysed the transfer of hydroxycinnamic acids from their CoA-esters to cyanidin 3-sophoroside, anthocyanidin 3,5-diglucosides, anthocyanidin 3-sophoroside-5-glucosides and delphinidin 3-glucoside. The other transferred the malonyl moiety from malonyl-Coa preferably to anthocyanidin 3-coumaroylglucoside-5-glucosides and anthocyanidin 3-glucosides, Anthocyanidin 3,5-diglucosides, anthocyanidin 3-sophoroside-5-glucosides, anthocyanidin 3-biosides and cyanidin 3,3'-diglucoside were less effective substrates for the malonyltransferase. The substrate specificity was rather broad, as anthocyanins which were not detected in cell cultures or plants of A, reptans were acylated as well. In vitro the hydroxycinnamoyltransferase transferred only one acyl group per anthocyanin molecule, while in vivo the main anthocyanins of callus, suspension cultures and flowers of A. replans contain two aromatic acyl groups per pigment molecule. The hydroxycinnamoyltransferase activity was totally absent in acyanic calli, while the malonyltransferase activity could be detected in two acyanic callus lines of A. reptans. The hydroxycinnamoyltransferase was inhibited by several divalent ions.