Biochemical Characterization of a Flavonoid O-methyltransferase from Perilla Leaves and Its Application in 7-Methoxyflavonoid Production

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.

Production of (2S)-sakuranetin from (2S)-naringenin in Escherichia coli by strengthening methylation process and cell resistance

“…Previous studies have confirmed that OsNOMT [ 21 ], SaOMT2 [ 22 ] and PfOMT3 [ 6 ] belong to the F7-OMTs family, and they have catalytic activity for converting (2 S )-naringenin to (2 S )-sakuranetin. In order to select the optimal F7-OMT, the production of (2 S )-sakuranetin at different (2 S )-naringenin concentrations with strains expressing F7-OMTs were compared.…”

“…(2 S )-Sakuranetin (7- O -methylated (2 S )-naringenin) is a 7- O -methylated flavonoid that is present in many plants, such as Oryza sativa [ 1 ], orange peel [ 2 ], and Piper lanceifolium Kunth [ 3 ]. It has been proved to have anti-inflammatory [ 4 ] (such as inhibiting 5ARII [ 5 ]), antimutation, anti- Helicobacter pylori [ 6 ], antidiabetic [ 7 ], antiviral (inhibiting viruses such as the influenza B/Lee/40 virus [ 8 ] and human rhinovirus 3 [ 9 ]), and anticonvulsant [ 10 ] properties. It can also exert protective effect on the brain, and can be used to treat Alzheimer's disease [ 11 ].…”

“…F7-OMTs are S -adenosylmethionine (SAM)-dependent flavonoid methyltransferases that can transfer the methyl group from SAM to the 7-OH of flavonoids [ 6 ]. The limited supply of methyl donor in E. coli can restrict the accumulation of (2 S )-sakuranetin.…”

Comparative Transcriptome Analysis of the Accumulation of Anthocyanins Revealed the Underlying Metabolic and Molecular Mechanisms of Purple Pod Coloration in Okra (Abelmoschus esculentus L.)

“…In addition to the classical members of the MBW complex, transcription factors of WRKY, NAC, MADS box, and bZIP families have also been reported to play important regulatory roles in anthocyanin biosynthesis [ 21 , 22 , 23 , 37 ]. Most of these transcription factors have been proved to indirectly regulate the production of anthocyanins via MBW complex, while bZIP family transcription factor SlHY5 could directly recognize and bind to the promoters of anthocyanin biosynthetic genes, CHS and DFR, to trigger the accumulation of anthocyanins by inducing the transcriptional activation of target genes [ 38 ].…”

Properties of Cell-Compatible Poly(vinyl alcohol) Hydrogels Cross-Linked with Hydrophobic Luteolin

“…We speculated that some hydrophobic biomolecules with phenolic groups would also have the potential to form hydrogen-bonded cross-links. Phenolic molecules have not been studied thus far, most likely because the strong self-aggregation tendency of hydrophobic biomolecules not only limits their medical applications, but also hinders the formation of hybrid gels with polymers such as PVA. − In addition, because of the differences in chemical properties from different numbers and positions of biomolecular phenolic groups, it is challenging to test hydrophobic biomolecules that can stably cross-link PVA molecular chains …”