Characterization of three distinct flavonol O-methyltransferases from Chrysosplenium americanum |
| |
Authors: | Vincenzo de Luca Ragai K. Ibrahim |
| |
Affiliation: | Department of Biology, Concordia University, 1455 deMaisonneuve Blvd., Montreal, Québec, Canada H3G 1M8 |
| |
Abstract: | The partially purified O-methyltransferase (OMT) system of Chrysosplenium americanum was found to catalyse the stepwise O-methylation of quercetin to its mono-, di- and trimethyl derivatives. It also utilized the partially methylated flavonol intermediates to form the next higher order of O-methylated products; thus indicating the involvement of several OMTs. The latter were resolved by chromatofocusing into three distinct peaks of enzyme activity which focused at pI values 4.8, 5.4 and 5.7. The former enzyme O-methylated quercetin at the 3-position, whereas the latter two O-methylated 3, 7-di-O-methyl quercetagetin at the 3′- and 6-positions, respectively. None of the focused enzymes accepted caffeic acid, or other flavonoids such as kaempferol or luteolin, as substrates; thus indicating specificity towards flavonols with 3′, 4′- substitution. The three OMTs had similar MWs and the Km values for their substrates were of the same order of magnitude. The biochemical role of these novel enzymes is discussed in relation to the biosynthesis of polymethylated flavonols in this tissue. |
| |
Keywords: | Saxifragaceae polymethylated flavonols enzymatic synthesis |
本文献已被 ScienceDirect 等数据库收录! |
|