title: Regiospecific methylation of naringenin to ponciretin by soybean O-methyltransferase expressed in Escherichia coli.
abstract: Flavonoids found in plants most likely undergo a variety of modification reactions such as hydroxylation, glycosylation, and/or methylation. Among these, O-methylation has an effect on the solubility and thus on the antimicrobial activity of the flavonoids. We analyzed the conversion of naringenin with a methyltransferase, SOMT-2, from Glycine max. SOMT-2 was expressed in Escherichia coli as a glutathion S-transferase fusion protein. E. coli harboring SOMT-2 was grown with daidzein, geninstein, apigenin, naringenin, and quercetin, respectively, and reaction products were analyzed with thin layer chromatography and HPLC. SOMT-2 could convert apigenin, daidzein, genistein, and quercetin into the corresponding 4'-O-methylated compounds such as acacetin, formononetin, biochanine A, and 4'-methylated quercetin whereas naringenin turned out to be the best substrate tested. SOMT-2 stoichiometically converted naringenin (4',5,7-trihyroxyflavanone) into a ponciretin (4'-methoxy-5,7-dihydroxyflavanone), whose structure was determined by NMR and LC/mass spectral analyses. Considering the reactions, SOMT-2 may have a regiospecific methylation activity, resulting in transforming 4'-hydroxyl group of flavonoids B-ring to 4'-methyl group.
authors.affiliation: Department of Molecular Biotechnology, Bio/Molecular Informatics Center, Konkuk University, 1 Hwayang-dong, Kwangjin-gu, Seoul 143-701, Korea.
authors.forename: Dae Hwan
authors.initials: DH
authors.lastname: Kim
authors.forename: Bong-Gyu
authors.initials: BG
authors.lastname: Kim
authors.forename: Youngshim
authors.initials: Y
authors.lastname: Lee
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Ryu
authors.forename: Yoongho
authors.initials: Y
authors.lastname: Lim
authors.forename: Hor-Gil
authors.initials: HG
authors.lastname: Hur
authors.forename: Joong-Hoon
authors.initials: JH
authors.lastname: Ahn
mesh_terms: D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics*; D044950:Flavanones / Q000737:chemistry* / Q000378:metabolism*; D005419:Flavonoids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013025:Glycine max / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity
chemical_list: D044950:Flavanones; D005419:Flavonoids; D011993:Recombinant Fusion Proteins; D008780:Methyltransferases; C005273:naringenin