Abstract
Ternatins, polyacylated anthocyanins accumulated in blue petal of butterfly pea, are delphinidin 3-(6''-malonyl)glucoside-3',5'-diglucoside (ternatin C5) derivatives. Independently purified 3'- and 5'-glucosyltransferase (3'GT and 5'GT) were characterized to be similar in biochemical properties. We isolated the cDNA, CtBGT1, based on the internal amino acid sequences of the purified 3'GT. The CtBGT1 encodes a polypeptide of 447 amino acids with a molecular mass of 48,649. The sequence indicates that CtBGT1 belongs to the UF3GT family. Surprisingly, the CtBGT1 sequence shows only 8% identity to the functionally related gentian 3'GT (AB076697). The recombinant CtBGT1 expressed in E. coli was found to catalyze the sequential glucosylations at 3'- and 5'-OH groups of delphinidin, resulting in the formation of ternatin C5. Although CtBGT1 express in mauve line petals accumulating delphinidin 3-(6''-malonyl)glucoside, it contains a stop codon in its ORF. These results proposed that novel UDP-glucose:anthocyanin 3',5'-glucosyltransferase encoded by CtBGT1 is involved in ternatin biosynthesis.
