Regiospecific methylation of naringenin to ponciretin by soybean O-methyltransferase expressed in Escherichia coli

J Biotechnol. 2005 Sep 23;119(2):155-62. doi: 10.1016/j.jbiotec.2005.04.004.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biotransformation
  • Chromatography, High Pressure Liquid
  • Cloning, Molecular
  • Escherichia coli / genetics*
  • Flavanones / chemistry*
  • Flavanones / metabolism*
  • Flavonoids / chemistry
  • Magnetic Resonance Spectroscopy
  • Methylation
  • Methyltransferases / genetics*
  • Methyltransferases / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Soybeans / enzymology*
  • Soybeans / genetics
  • Substrate Specificity

Substances

  • Flavanones
  • Flavonoids
  • Recombinant Fusion Proteins
  • Methyltransferases
  • naringenin