Abstract
AA5/7GTs continued to catalyze the glucosyltransferase reaction until 48 h of incubation at 30oC. Native AA5GT (kcat for Cy3G = 0.06 s-1, kcat for VG = 0.01 s-1, Km for Cy3G = 13.0 μM and Km for VG = 46.5 μM) had similar kinetic parameters to recombinant AA5GT (kcat for Cy3G = 0.07 s-1, kcat for VG = 0.01 s-1, Km for Cy3G = 6.5 μM and Km for VG = 51.9 μM), but AA7GT (kcat for Cy3G = 0.30 s-1, kcat for VG = 0.11 s-1, Km for Cy3G = 22.5 μM and Km for VG = 121.1 μM) showed slightly different kinetic parameters to AA5GT. AA5/7GTs showed a strict acceptor preference for anthocyanidins glycosylated at 5 position. By contrast, these AAGTs could use various acyl-glucose molecules as donor substrates. To confirm the sub-cellular localization of AA5/7GTs, GFP fusion constructs containing the predicted transit peptide sequences of AA5/7GTs were introduced into onion epidermal cells by microprojectile bombardment. We observed a close correspondence in the distribution pattern for transit-peptide:GFP with that of control vacuolar protein. This research was partially supported by the Research and Development Program for New Bio-industry Initiatives.
