Abstract
Apigenin, a widely distributed flavone, exhibits excellent antioxidant, anti-inflammatory, and antitumor properties. In addition, the methylation of apigenin is generally considered to result in better absorption and greatly increased bioavailability. Here, four putative Class II methyltransferase genes were identified from the transcriptome sequences generated from the liverwort species Plagiochasma appendiculatum. Each was heterologously expressed as a His-fusion protein in Escherichia coli and their methylation activity against apigenin was tested. One of the four Class II OMT enzymes named 4′-O-methyltransferase (Pa4′OMT) was shown to react effectively with apigenin, catalyzing its conversion to acacetin. Besides the favorite substrate apigenin, the recombinant PaF4′OMT was shown to catalyze luteolin, naringenin, kaempferol, quercetin, genistein, scutellarein, and genkwanin to the corresponding 4′-methylation products. In vivo feeding experiments indicated that PaF4′OMT could convert apigenin to acacetin efficiently in E. coli and approximately 88.8 µM (25.2 mg/L) of product was synthesized when 100 µM of apigenin was supplemented. This is the first time that a Class II plant O-methyltransferase has been characterized in liverworts.
Highlights
Flavonoids are a family composed of various polyphenolic compounds synthesized by plant species
Enzyme-catalyzed synthesis of acacetin can be achieved by the para-O-methylation of apigenin using S-adenosyl-L-methionine as a methyl donor catalyzed by O-methyltransferases (OMTs)
PaF4 catalyzed the O-methylation of apigenin to form acacetin in E. coli, has been characterized in was synthesized
Summary
Flavonoids are a family composed of various polyphenolic compounds synthesized by plant species. O-methyltransferases are known to be involved in the reaction transforming methyl to hydroxy groups of phenylpropanoids and flavonoids. O-methyltransferases) are cation-independent enzymes capable of methylating flavonoids, but CCoAOMT possess two vicinal hydroxyl groups phenylpropanoid-derived and their methylation affects the precursors meta-hydroxyl both 3-hydroxyl-and. For the production of acacetin, direct C-4′ methylation of apigenin drawbacks: catalytic means, conditions, time, protection of unwanted and is impossibleharsh by chemical due atolong the reaction higher acidity of C-7 hydroxy group. A description is given of the isolation of four Plagiochasma appendiculatum Class II OMTs, one Liverworts produce methylated flavonoids, compounds, and bis-bibenzyls. PaF4 catalyzed the O-methylation of apigenin to form acacetin in E. coli, has been characterized in was synthesized This is the first time that a Class II plant O-methyltransferase, which catalyzed the liverworts.
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