Abstract
Methylation is a common structural modification that can alter and improve the biological activities of natural compounds. O-Methyltransferases (OMTs) catalyze the methylation of a wide array of secondary metabolites, including flavonoids, and are potentially useful tools for the biotechnological production of valuable natural products. An OMT gene (PfOMT3) was isolated from perilla leaves as a putative flavonoid OMT (FOMT). Phylogenetic analysis and sequence comparisons showed that PfOMT3 is a class II OMT. Recombinant PfOMT3 catalyzed the methylation of flavonoid substrates, whereas no methylated product was detected in PfOMT3 reactions with phenylpropanoid substrates. Structural analyses of the methylation products revealed that PfOMT3 regiospecifically transfers a methyl group to the 7-OH of flavonoids. These results indicate that PfOMT3 is an FOMT that catalyzes the 7-O-methylation of flavonoids. PfOMT3 methylated diverse flavonoids regardless of their backbone structure. Chrysin, naringenin and apigenin were found to be the preferred substrates of PfOMT3. Recombinant PfOMT3 showed moderate OMT activity toward eriodictyol, luteolin and kaempferol. To assess the biotechnological potential of PfOMT3, the biotransformation of flavonoids was performed using PfOMT3-transformed Escherichia coli. Naringenin and kaempferol were successfully bioconverted to the 7-methylated products sakuranetin and rhamnocitrin, respectively, by E. coli harboring PfOMT3.
Highlights
Flavonoids are a structurally diverse group of plant secondary metabolites, which play important roles in plant growth and defense against biotic and abiotic stresses [1,2,3]
An OMT gene was identified as a putative flavonoid OMT (FOMT), and named P. frutescens OMT3 (PfOMT3, GenBank accession number: MT909556)
To characterize its biochemical properties, PfOMT3 was expressed in E. coli and affinity purified
Summary
Flavonoids are a structurally diverse group of plant secondary metabolites, which play important roles in plant growth and defense against biotic and abiotic stresses [1,2,3]. A wide range of modifications of the hydroxyl groups, such as glycosylation, methylation and prenylation, offer structural diversity to flavonoids, and affect their physiological functions and biological activities [1,4]. The methylation of flavonoids can alter and/or improve their physicochemical properties and biological activities [6,7,8,9]. Methylation has been suggested to be a simple and effective way to enhance the metabolic resistance and transport of ingested flavonoids [9,11]. Methylation is important in the antimicrobial activity of flavonoids. Ponciretin (40 -O-methylnaringenin) and sakuranetin (7-O-methylnaringenin) were shown to have antibacterial activity against Helicobacter pylori [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
