Tobacco Ntomt2 Revisited: Multiple O-Methylation of Quercetin is Catalyzed by a Single Gene Product
2016
Tobacco NtOMT2 was previously reported as an inducible, o-diphenol O-methyltransferase (OMT) that exhibits
similar preferences towards quercetin and caffeic acid as substrates. In this report, we further examine the substrate
specificity of NtOMT2 based on enzyme assays, kinetic data and phylogenetic analysis. We demonstrate that
NtOMT2 is a flavonol OMT that catalyzes multiple O-methylation of the flavonol quercetin giving rise to its mono-,
di- and trimethyl ether derivatives. Mono-methylation of quercetin on the 3-, 3′-/4′- and 7-hydroxyl groups occurs in
a random fashion according to the physio-chemical properties of their hydroxyl groups, together with their similar
binding energies in the NtOMT2 binding pocket. Homology modeling of NtOMT2 with the Medicago sativa COMT
as a template indicates that the H-bonding network between the functional hydroxyl groups and the neighboring
residues allowed NtOMT2 to establish a number of energetically similar binding arrangements with slightly different
binding modes; thus resulting in a random multiple methylation. NtOMT2 functions as a proximity and orientation
agent in using the general base catalysis for multiple methylation of quercetin. This is the first report to indicate that
quercetin multiple methylation is catalyzed by a single gene product.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
43
References
0
Citations
NaN
KQI