Identification and Characterization of Two New 1- O-Acyl-glucose-ester Forming Glucosyltransferases from Erigeron breviscapus.

Two versatile UDP-glucosyltransferases, UGT75L25 and UGT75X1, were isolated from Erigeron breviscapus. The enzymes display high sequence identity to flavonoid 7- O-glucosyltransferase from Malus species and cluster to the phylogenetic group L of plant glucosyltransferases, also involved in the formation of hydroxycinnamoyl glucose esters, which are used as bifunctional donors in the glucosylation or acylation of anthocyanins. The enzymes, functionally expressed in Escherichia coli, exhibit broad substrate specificity toward 21 structurally diverse types of phenolic acids, including (hydroxy)cinnamates, vanillic acid, 3-hydroxycoumarin, and 7-hydroxyflavonoids. The catalytic characteristics of UGT75L25 and UGT75X1 were exploited to generate the corresponding acyl-glucose-esters or glucosides with high efficiency. These findings demonstrate the significant potential of acyl-glucose-esters in the further enzymatic synthesis of bioactive anthocyanins.