Simple and Efficient Production of Highly Soluble Daidzin Glycosides by Amylosucrase from Deinococcus geothermalis.

Transglycosylation of amylosucrase from Deinococcus geothermalis (DGAS) was performed using daidzin (daidzein-7-O-glucoside). Unlike cyclodextrin glucanotransferase, DGAS led to the production of new daidzin glucosides with high conversion yields (89%). Structures of these daidzin glucosides (i.e., DA2 and DA3) were daidzein-7-O-α-d-glucopyranosyl-(4 → 1)-O-β-d-glucopyranoside (daidzin-4″-O-α-d-glucopyranoside) and daidzein-4'-O-α-d-glucopyranosyl-7-O-α-d-glucopyranosyl-(1 → 4)-O-β-d-glucopyranoside (daidzin-4',4″-O-α-d-diglucopyranoside), respectively. DA2 and DA3 showed increased solubility of 15.4 mM (127-fold) and 203.3 mM (1686-fold) compared with daidzin, respectively. Kinetic studies revealed Vmax of 1.0 μM/min and K'm of 175 μM for DA3 production based on nonlinear regression. DGAS exhibited substrate inhibition behavior at high sucrose concentrations (700-1500 mM). Taken together, these findings indicate that DGAS can attach a glucose unit to a free C4'-OH via an α-linkage and then produce highly water-soluble isoflavone glycosides with a simple donor, moderate reaction conditions, less waste production, and high yield compared with that observed using the existing processes and enzymes.