Involved in the acylation of the 6'' position of the 3-O-glucose residue of anthocyanin. Also able to use flavonol 3-glucosides as the acyl acceptor. kcat is 6.9 sec(-1) for p-coumaroyl-CoA. kcat is 7.7 sec(-1) for feruloyl-CoA. kcat is 8.5 sec(-1) for caffeoyl-CoA. kcat is 6.9 sec(-1) for cyanidin 3-glucoside. kcat is 7.5 sec(-1) for pelargonidin 3-glucoside. kcat is 6.3 sec(-1) for malvidin 3-glucoside. kcat is 0.9 sec(-1) for quercetin 3-glucoside. kcat is 0.8 sec(-1) for kaempferol 3-glucoside. kcat is 2.0 sec(-1) for kaempferol 7-glucoside. kcat is <0.001 sec(-1) for cyanidin 3,5-diglucoside. kcat is <0.001 sec(-1) for pelargonidin 3,5-diglucoside. Highly expressed in flowers, and leaves. Lower levels of expression in stems, roots and siliques. No visible phenotype, probably due to the redundancy with 3AT1. Belongs to the plant acyltransferase family.