Identification and recombinant production of a flavonoid glucosyltransferase with broad substrate specificity from Vaccinium corymbosum

Glucosyltransferases (GTs) are enzymes that use UDP-glucose to glucosylate wide variety of substrates, including the aglycones of anthocyanins. Anthocyanins are glycosylated polyphenolic plant pigments possessing potential health benefits to humans. The berries of Vaccinium species plants are rich in anthocyanins. Although the flavonoid content of bilberries is well characterized, the enzymes responsible for carrying out anthocyanin modifications are not thoroughly studied. In this study, a predicted sequence of an anthocyanin glucosyltransferase was identified from the genomic data of Vaccinium corymbosum. The codon-optimized gene sequence of the protein was integrated into the genome of P. pastoris. Constitutive expression in yeast extract-peptone-dextrose based media gave satisfactory amount of recombinant protein. The enzyme activity assays revealed that the V. corymbosum GT transferred glucosyl moieties to up to three positions of diverse flavonoids, such as naringenin, kaempferol, eriodictyol and cyanidin 3-O-glucoside, being therefore a rather unique enzyme among GTs described so far. The enzyme preferred cyanidin 3-O-glucoside, peonidin 3-O-glucoside and eriodictyol as substrates. This enzyme could find application in biotechnological production of glucosylated flavonoids.