UDP-Glycosyltransferases Engineering Coupled with UDPG Regeneration Facilitate the Efficient Conversion of Mogroside V

Mogroside V is a triterpene, a natural high-intensity sweetener, isolated from the fruits of Siraitia grosvenorii. Selective glycosylation of mogrol is a feasible approach for the biosynthesis of mogroside V. In this study, glycosyltransferase UGTM1 and UGTM2 were engineered to UGTM1-3 and UGTM2-4, which selectively and directly transfer glucose from UDPG to 3'-hydroxyl and 24'-hydroxyl groups and their branch chains of the mogrol moiety for the biosynthesis of mogroside V. The enzyme activities of UGTM1-3 and UGTM2-4 were enhanced 2.88 and 3.60 times, respectively. To eliminate the need for UDPG and improve productivity, a UDPG regeneration system was introduced to couple with the UGTs. Finally, mogrol was directly converted to mogroside V by UGTM1-3, UGTM2-4, and AtSUS1 with a conversion rate of 18.2% without the exogenous addition of UDPG. This study provides an in vitro multienzyme cascade catalytic system for the efficient conversion of mogroside V.