Glucosylation of hydroxyflavones by glucosyltransferases from Phytolacca americana

Cell suspension cultures of Phytolacca americana can glucosylate 6- and 7-hydroxyflavone, but not 5-hydroxyflavone. In order to identify the enzymes responsible for these transformations, glucosyltransferases (GTs) from P. americana were overexpressed in Escherichia coli and purified. The purified PaGT3 enzyme could glucosylate 6- and 7-hydroxyflavone when incubated with UDP-glucose, a glucosyl donor molecule, but PaGT2 could conjugate a glucose moiety only to 6-hydroxyflavone. E. coli cells expressing PaGT2 and 3 could also be utilized for the glucosylation of hydroxyflavones. The glucoside products which had accumulated in the medium of overnight E. coli cell cultures were isolated using hydrophobic resins. This methodology might be suitable for the glucosylation of aglycones with important health-related properties.

PaGT3, a glucosyltransferase 3 enzyme isolated from Phytolacca americana, could glucosylate 6- and 7-hydroxyflavone. PaGT2, a glucosyltransferase 2 enzyme isolated from P. americana, could glucosylate 6-hydroxyflavone. However, 5-hydroxyflavone was not a substrate of PaGT2 or 3.Figure optionsDownload as PowerPoint slideHighlights
► Two glucosyltransferases from P. americana (PaGT2, 3) were overexpressed and purified.
► PaGT3 could glucosylate 6- and 7-hydroxyflavones to yield the corresponding β-glucosides.
► PaGT2 could glucosylate 6-hydroxyflavones to yield the corresponding β-glucoside.
► 5-Hydroxyflavone was not a substrate for PaGT2 nor 3.