Abstract
Sucrose synthase (SuSy, EC 2.4.1.13) is a unique glycosyltransferase
(GT) for developing cost-effective glycosylation processes. Up to now,
some SuSys derived from plants and bacteria have been used to recycle
uridine 5’-diphosphate glucose in the reactions catalyzed by Leloir GTs.
In this study, after sequence mining and experimental verification, a
SuSy from Micractinium conductrix(Mc SuSy), a single-cell
green alga, was identified. In the direction of sucrose cleavage, the
optimum temperature and pH of the recombinant Mc SuSy were 60 °C
and pH 7.0. The mutations of the predicted N -terminal
phosphorylation site (S31D) and the QN motif (K684T and N685D)
significantly stimulated the activity of Mc SuSy. When the mutant
S31D/684T/685D of Mc SuSy, with the highest activity, was applied
by coupling the engineered yeast glycosyltransferase UGT51 in a one-pot
two-enzyme reaction, 8 mM protopanaxadiol was transformed into 6.02 mM
(3.75 g/L) ginsenoside Rh2 within 3 h at 37 °C. The yield was comparable
to the control reaction of AtSuSy1 from Arabidopsis thaliana .
This work reveals the lower eukaryotes as a promising resource for SuSys
of industrial interest.