Enzymatic synthesis of myricetin 3-O-galactoside through a whole-cell biocatalyst

OBJECTIVE: Myricetin 3-O-galactoside is an active compound with pharmaceutical potential. The insufficient supply of this compound becomes a bottleneck in the druggability study of myricetin 3-O-galactoside. Thus, it is necessary to develop a biosynthetic process for myricetin 3-O-galactoside through metabolic engineering. METHODS: Two genes OcSUS1 and OcUGE1 encoding sucrose synthase and UDP-glucose 4-epimerase were introduced into BL21(DE3) to reconstruct a UDP-D-galactose (UDP-Gal) biosynthetic pathway in Escherichia coli. The resultant chassis strain was able to produce UDP-Gal. Subsequently, a flavonol 3-O-galactosyltransferase DkFGT gene was transformed into the chassis strain producing UDP-Gal. An artificial pathway for myricetin 3-O-galactoside biosynthesis was thus constructed in E. coli. RESULTS: The obtained engineered strain was demonstrated to be capable of producing myricetin 3-O-galactoside, reaching 29.7 mg/L. CONCLUSION: Biosynthesis of myricetin 3-O-galactoside through engineered E. coli could be achieved. This result lays the foundation for the large-scale preparation of myricetin 3-O-galactoside.