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A cDNA encoding UDP-glucose: formononetin 7- O-glucosyltransferase, designated UGT73F1, was cloned from yeast extract-treated Glycyrrhiza echinata L. cell-suspension cultures using probes from Scutellaria baicalensis UDP-glucose: flavonoid 7- O-glucosyltransferase. The open reading frame of the UGT73F1 cDNA encodes a 441-amino-acid protein with a predicted molecular mass of 48.7 kDa. The deduced amino acid sequence showed that the protein is related to the stress-inducible glucosyltransferases. UGT73F1 mRNA was not detected in untreated G. echinata cultures but was transiently induced by treatment with yeast extract. Recombinant UGT73F1 was expressed as a histidine-tag fusion protein in Escherichia coli and purified to near homogeneity by nickel chelate chromatography. The purified recombinant enzyme was selective for isoflavonoid, formononetin and daidzein as substrates, while flavonoids and various tested non-flavonoid compounds were poor substrates.

The Eucalyptus perriniana cultured cells are widely used to biotransform a variety of compounds. The glucosyltransferase activity of a crude protein extract of E. perriniana cultured cells was maximized when cell growth was in the pre-logarithmic to logarithmic phase. We cloned a cDNA encoding glucosyltransferase (EPGT) from E. perriniana cultured cells by RT-PCR using a degenerated primer and RACE-PCR. The cDNA contained an open reading frame encoding 467 amino acids with a calculated molecular mass of 51.6 kDa. The consensus sequence of the plant glucosyltransferases was included in the deduced amino acid sequence. The amino acid sequence of EPGT showed a high identity to glucosyltransferases from tobacco and petunia. The recombinant EPGT was expressed in Escherichia coli and its substrate specificity was examined using UDP-[U-14 C] glucose. Cinnamic acid was the best sugar acceptor in the compounds tested.

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