Recombinant Expression and Characterization of an Alkali-tolerant UDP-Glycosyltransferase from <i>Solanum lycopersicum</i> and Its Biosynthesis of Gastrodin

Glycosyltransferases can take small molecular weight compounds as receptor substrates and uridine 5'diphosphate (UDP) as donors [14].The research report shows that gastrodin can be biosynthesized by glycosylation of p-hydroxybenzyl alcohol by UDP-glycosyltransferase [13].Therefore, the catalytic activity of UGT plays a decisive role in the biosynthesis of gastrodin.However, glycosyltransferase used for biosynthesis of gastrodin in the metabolic pathway of Gastrodia elata is unknown.Although it has been reported that a single gene encoding glycosyltransferase may participate in the natural biosynthesis pathway of gastrodin [11], the sequence of natural UGT used for gastrodin biosynthesis is still unclear [12,13].In this study, UDPglycosyltransferase from Solanum lycopersicum (SlyUGT) was overexpressed in E. coli BL21(DE3), and the expression conditions of the enzyme SlyUGT were optimized.Meanwhile, its enzymatic characteristics were determined with pHBA as glycosyl receptor and UDP-glucose as glycosyl donor.In addition, the biosynthesis conditions of gastrodin by SlyUGT were also studied.The results suggested that SlyUGT had potential application value in gastrodin biosynthesis.Gastrodin is the main bioactive component of Gastrodia elata, which has many excellent pharmacological activities.In this study, UDP-glycosyltransferase from Solanum lycopersicum (SlyUGT) was overexpressed, purified and characterized, and it can be used for biosynthesis of gastrodin.The SlyUGT maximum enzyme activity was 29.48 mU/ml, and its relative molecular weight was about 78.5 kDa.The SlyUGT was purified 16.1-fold by GST affinity resin with an overall recovery of 53.9% and specific activity of 20.9 mU/mg.The optimal temperature of SlyUGT was 40 o C, and it exhibited excellent thermal stability at 35 o C and 40 o C. Furthermore, the SlyUGT had the highest activity at pH 9.5 and good pH stability at pH 5.5-10.5.The enzyme can tolerate low concentrations of DMSO and UDP.In addition, the values of K M and V max were found to be 0.65 mM and 74.60 mU/mg respectively.The SlyUGT could convert pHBA into gastrodin by using UDP-glucose as a sugar donor.Under the optimal biosynthesis conditions, the gastrodin production reached 559.83 mg/l, and the corresponding molar conversion rate reached 97.82%.The results showed that SlyUGT has potential application value in the preparation of gastrodin.