Publications

• Enzymatic synthesis of polymethylated flavonols in Chrysosplenium americanum. I. Partial purification and some properties of S-adenosyl-L-methionine:flavonol 3-, 6-, 7-, and 4'-O-methyltransferases.

  De Luca V., Ibrahim R.K.

  Four novel flavonol O-methyltransferases (OMTs) were partially purified from Chrysosplenium americanum by precipitation with ammonium sulfate, successive chromatography on Sephacryl S-200 and hydroxylapatite, and chromatofocusing on Polybuffer ion exchanger. They exhibited strict position specific ... >> More

  Four novel flavonol O-methyltransferases (OMTs) were partially purified from Chrysosplenium americanum by precipitation with ammonium sulfate, successive chromatography on Sephacryl S-200 and hydroxylapatite, and chromatofocusing on Polybuffer ion exchanger. They exhibited strict position specificity for positions 3 of quercetin, 7 of 3-methylquercetin, 4' of 3,7-dimethylquercetin, and 6 of 3,7,3'-trimethylquercetagetin. None of these enzymes reacted with phenylpropanoids, flavones, dihydroflavonols, or any of their glucosides. Except for the 7-OMT whose activity was lost during chromatofocusing, the other enzymes had apparent pI values of 4.8, 5.4, and 5.7 for the 3-, 4'-, and 6-OMTs, respectively. They had similar molecular weights (Mr 57,000) and their pH optima varied between 7.8 and 9.0, with a shift in optimal activity from lower to higher pH with increasing level of substrate methylation. Unlike the 3 and 4' enzymes, the 6-OMT showed an absolute requirement for Mg2+ whose activation was saturable and was inhibited by EDTA. The in vitro stepwise O-methylation of quercetin----3-methylquercetin----3,7-dimethylquercetin----3 ,7, 4'-trimethylquercetin tends to suggest a coordinated sequence of methyl transfers in this tissue. << Less

  Arch Biochem Biophys 238:596-605(1985) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Polymethylated myricetin in trichomes of the wild tomato species Solanum habrochaites and characterization of trichome-specific 3'/5'- and 7/4'-myricetin O-methyltransferases.

  Schmidt A., Li C., Shi F., Jones A.D., Pichersky E.

  Flavonoids are a class of metabolites found in many plant species. They have been reported to serve several physiological roles, such as in defense against herbivores and pathogens and in protection against harmful ultraviolet radiation. They also serve as precursors of pigment compounds found in ... >> More

  Flavonoids are a class of metabolites found in many plant species. They have been reported to serve several physiological roles, such as in defense against herbivores and pathogens and in protection against harmful ultraviolet radiation. They also serve as precursors of pigment compounds found in flowers, leaves, and seeds. Highly methylated, nonglycosylated derivatives of the flavonoid myricetin flavonoid, have been previously reported from a variety of plants, but O-methyltransferases responsible for their synthesis have not yet been identified. Here, we show that secreting glandular trichomes (designated types 1 and 4) and storage glandular trichomes (type 6) on the leaf surface of wild tomato (Solanum habrochaites accession LA1777) plants contain 3,7,3'-trimethyl myricetin, 3,7,3',5'-tetramethyl myricetin, and 3,7,3',4',5'-pentamethyl myricetin, with gland types 1 and 4 containing severalfold more of these compounds than type 6 glands and with the tetramethylated compound predominating in all three gland types. We have also identified transcripts of two genes expressed in the glandular trichomes and showed that they encode enzymes capable of methylating myricetin at the 3' and 5' and the 7 and 4' positions, respectively. Both genes are preferentially expressed in secreting glandular trichome types 1 and 4 and to a lesser degree in storage trichome type 6, and the levels of the proteins they encode are correspondingly higher in types 1 and 4 glands compared with type 6 glands. << Less

  Plant Physiol. 155:1999-2009(2011) [PubMed] [EuropePMC]

  This publication is cited by 13 other entries.