Publications

• Flavonoid 3'-O-methyltransferase from rice: cDNA cloning, characterization and functional expression.

  Kim B.-G., Lee Y., Hur H.-G., Lim Y., Ahn J.-H.

  Plant O-methyltransferases (OMTs) are known to be involved in methylation of plant secondary metabolites, especially phenylpropanoid and flavonoid compounds. An OMT, ROMT-9, was cloned and characterized from rice using a reverse transcriptase polymerase chain reaction (RT-PCR). The blast results f ... >> More

  Plant O-methyltransferases (OMTs) are known to be involved in methylation of plant secondary metabolites, especially phenylpropanoid and flavonoid compounds. An OMT, ROMT-9, was cloned and characterized from rice using a reverse transcriptase polymerase chain reaction (RT-PCR). The blast results for ROMT-9 showed a 73% identity with caffeic acid OMTs from maize and Triticum aestivum. ROMT-9 was expressed in Escherichia coli and its recombinant protein was purified using affinity chromatography. It was then tested for its ability to transfer the methyl group of S-adenosyl-l-methionine to the flavonoid substrates, eriodictyol, luteolin, quercetin, and taxifolin, all of which have a 3'-hydroxyl functional group. The reaction products were analyzed using TLC, HPLC, HPLC/MS, and NMR spectroscopy. The NMR analysis showed that ROMT-9 transferred the methyl group specifically to the 3'-hydroxyl group of quercetin, resulting in the formation of its methoxy derivative. Furthermore, ROMT-9 converted flavonoids containing the 3'-hydroxy functional group such as eriodictyol, luteolin, quercetin and taxifolin into the corresponding methoxy derivatives, suggesting that ROMT-9 is an OMT with strict specificity for the 3'-hydroxy group of flavonoids. << Less

  Phytochemistry 67:387-394(2006) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• The flavonoid biosynthetic pathway in Arabidopsis: Structural and genetic diversity.

  Saito K., Yonekura-Sakakibara K., Nakabayashi R., Higashi Y., Yamazaki M., Tohge T., Fernie A.R.

  Flavonoids are representative plant secondary products. In the model plant Arabidopsis thaliana, at least 54 flavonoid molecules (35 flavonols, 11 anthocyanins and 8 proanthocyanidins) are found. Scaffold structures of flavonoids in Arabidopsis are relatively simple. These include kaempferol, quer ... >> More

  Flavonoids are representative plant secondary products. In the model plant Arabidopsis thaliana, at least 54 flavonoid molecules (35 flavonols, 11 anthocyanins and 8 proanthocyanidins) are found. Scaffold structures of flavonoids in Arabidopsis are relatively simple. These include kaempferol, quercetin and isorhamnetin for flavonols, cyanidin for anthocyanins and epicatechin for proanthocyanidins. The chemical diversity of flavonoids increases enormously by tailoring reactions which modify these scaffolds, including glycosylation, methylation and acylation. Genes responsible for the formation of flavonoid aglycone structures and their subsequent modification reactions have been extensively characterized by functional genomic efforts - mostly the integration of transcriptomics and metabolic profiling followed by reverse genetic experimentation. This review describes the state-of-art of flavonoid biosynthetic pathway in Arabidopsis regarding both structural and genetic diversity, focusing on the genes encoding enzymes for the biosynthetic reactions and vacuole translocation. << Less

  Plant Physiol. Biochem. 72:21-34(2013) [PubMed] [EuropePMC]

• Characterization of two cDNA clones which encode O-methyltransferases for the methylation of both flavonoid and phenylpropanoid compounds.

  Gauthier A., Gulick P.J., Ibrahim R.K.

  Enzymatic O-methylation of phenylpropanoid and flavonoid compounds is believed to be catalyzed by distinct classes of O-methyltransferases [EC 2.1.1.6x]. The O-methylated derivatives of phenylpropanoids and flavonoids play an important role in lignification and as antimicrobial compounds, respecti ... >> More

  Enzymatic O-methylation of phenylpropanoid and flavonoid compounds is believed to be catalyzed by distinct classes of O-methyltransferases [EC 2.1.1.6x]. The O-methylated derivatives of phenylpropanoids and flavonoids play an important role in lignification and as antimicrobial compounds, respectively. Two cDNA clones, OMT1 and OMT2, which differ in three amino acid residues were isolated and characterized from the semiaquatic freshwater weed Chrysosplenium americanum (Saxifragaceae). These two novel cDNA clones encode enzymes which catalyze the 3'-O-methylation of the flavonoid aglycones luteolin and quercetin, although they also catalyze the efficient 3/5-O-methylation of the phenylpropanoids caffeic and 5-hydroxyferulic acids, respectively. Both recombinant proteins were partially purified from an Escherichia coli expression system and their kinetic parameters were compared using two flavonoids and two phenylpropanoids as substrates. Although both gene products methylate caffeic acid and 5-hydroxyferulic acid to a similar extent, they exhibit a threefold higher affinity for and a four-to sixfold increase in turnover of flavonoid compounds. The gene product of OMT1 accepts the flavonoid substrates luteolin and quercetin for methylation at a higher rate than that of OMT2, as indicated by a two-to threefold increase in its Vmax values and turnover ratios. The fact that C. americanum accumulates a variety of highly methylated flavonols and exhibits little lignification suggests that these two flavonoid OMT clones have retained their ability to O-methylate phenylpropanoids as well. These results are discussed in relation to differences in the amino acid sequences of these two clones, as well as with other O-methyltransferases, and the evolutionary divergence of these genes in plants. << Less

  Arch. Biochem. Biophys. 351:243-249(1998) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.