Sequential O-methylation of tricetin by a single gene product in wheat.
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.
Zhou
Jian-Min
JM
Plant Biochemistry Laboratory, Concordia University, Montréal, Quebec, Canada H4B 1R6.
Gold
Nicholas D
ND
Martin
Vincent J J
VJ
Wollenweber
Eckhard
E
Ibrahim
Ragai K
RK
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*
D002867:Chromones; D018076:DNA, Complementary; D010940:Plant Proteins; D011994:Recombinant Proteins; D019800:Phenol; C469689:tricetin; D008780:Methyltransferases