title: Sequential O-methylation of tricetin by a single gene product in wheat.
abstract: Flavonoid compounds are ubiquitous in nature. They constitute an important part of the human diet and act as active principles of many medicinal plants. Their O-methylation increases their lipophilicity and hence, their compartmentation and functional diversity. We have isolated and characterized a full-length flavonoid O-methyltransferase cDNA (TaOMT2) from a wheat leaf cDNA library. The recombinant TaOMT2 protein was purified to near homogeneity and tested for its substrate preference against a number of phenolic compounds. Enzyme assays and kinetic analyses indicate that TaOMT2 exhibits a pronounced preference for the flavone, tricetin and gives rise to three methylated enzyme reaction products that were identified by TLC, HPLC and ESI-MS/MS as its mono-, di- and trimethyl ether derivatives. The sequential order of tricetin methylation by TaOMT2 is envisaged to proceed via its 3'-mono--->3',5'-di--->3',4',5'-trimethyl ether derivatives. To our knowledge, this is the first report of a gene product that catalyzes three sequential O-methylations of a flavonoid substrate.
authors.affiliation: Plant Biochemistry Laboratory, Concordia University, Montréal, Quebec, Canada H4B 1R6.
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Zhou
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Gold
authors.forename: Vincent J J
authors.initials: VJ
authors.lastname: Martin
authors.forename: Eckhard
authors.initials: E
authors.lastname: Wollenweber
authors.forename: Ragai K
authors.initials: RK
authors.lastname: Ibrahim
mesh_terms: D002867:Chromones / Q000737:chemistry*; D018076:DNA, Complementary / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D015723:Gene Library; D008745:Methylation; D008780:Methyltransferases / Q000737:chemistry*; D008969:Molecular Sequence Data; D019800:Phenol / Q000737:chemistry; D010802:Phylogeny; D018515:Plant Leaves; D010940:Plant Proteins / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry; D013379:Substrate Specificity; D014908:Triticum / Q000378:metabolism*
chemical_list: D002867:Chromones; D018076:DNA, Complementary; D010940:Plant Proteins; D011994:Recombinant Proteins; D019800:Phenol; C469689:tricetin; D008780:Methyltransferases