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3 S-adenosyl-L-methionine + tricetin = 3 S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
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S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin = S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
S-adenosyl-L-methionine + 3'-hydroxyflavone = S-adenosyl-L-homocysteine + 3'-methoxyflavone
S-adenosyl-L-methionine + 3'-O-methyltricetin = S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
S-adenosyl-L-methionine + tricetin = S-adenosyl-L-homocysteine + 3'-O-methyltricetin
S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin = S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
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S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin = S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
mechanism for the sequential methylation of tricetin, overview
S-adenosyl-L-methionine + 3'-hydroxyflavone = S-adenosyl-L-homocysteine + 3'-methoxyflavone
unique structural features of TaOMT2 which permit the stepwise methylation of tricetin is disclosed. Substrate binding is mediated by an extensive network of H-bonds and van der Waals interactions. The partly buried tricetin active site, as well as proximity and orientation effects ensure sequential methylation of the substrate within the same pocket. Stepwise methylation of tricetin involves deprotonation of its hydroxyl groups by a His262-Asp263 pair followed by nucleophilic attack of SAM-methyl groups
S-adenosyl-L-methionine + 3'-hydroxyflavone = S-adenosyl-L-homocysteine + 3'-methoxyflavone
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S-adenosyl-L-methionine + 3'-O-methyltricetin = S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
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S-adenosyl-L-methionine + 3'-O-methyltricetin = S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
mechanism for the sequential methylation of tricetin, overview
S-adenosyl-L-methionine + tricetin = S-adenosyl-L-homocysteine + 3'-O-methyltricetin
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S-adenosyl-L-methionine + tricetin = S-adenosyl-L-homocysteine + 3'-O-methyltricetin
mechanism for the sequential methylation of tricetin, overview
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3 S-adenosyl-L-methionine + tricetin
3 S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
S-adenosyl-L-methionine + 3'-O-methyltricetin
S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
S-adenosyl-L-methionine + 5-hydroxyferulic acid
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Substrates: second most preferred substrate with 78% activity compared to tricetin
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3'-O-methyltricetin
additional information
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3 S-adenosyl-L-methionine + tricetin
3 S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: overall reaction
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3 S-adenosyl-L-methionine + tricetin
3 S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: TaOMT1 (TaCOMT1) catalyzes the sequential methylation of tricetin to its 3'-O-monomethyl-derivative (selgin), 3',5'-O-dimethyl-derivative (tricin) and 3',4',5'-O-trimethyl derivative. 3',5'-O-dimethyltricetin appears to be the major reaction product. The enzyme also catalyzes methylation of luteolin, quercetin and eriodictyol
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3 S-adenosyl-L-methionine + tricetin
3 S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: the enzyme catalyzes three sequential O-methylations, forming 3'-O-methyltricetin, 3',5'-dimethyltricetin and 3',4',5'-O-trimethyltricetin. Tricetin is the preferred substrate. Also catalyzes the methylation of 5-hydroxyferulic acid, luteolin, quercetin, eriodyctiol, quercetagetin, taxifolin, gossypetin and myricetin. TaOMT2 is a flavonoid, B-ring-specific O-methyltransferase with a preference for flavones > dihydroflavones > flavonols that possess at least two, B-ring hydroxyl groups
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S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: -
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S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: the enzyme catalyzes three sequential O-methylations, forming 3'-O-methyltricetin, 3',5'-dimethyltricetin and 3',4',5'-O-trimethyltricetin. Tricetin is the preferred substrate
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S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + 3'-O-methyltricetin
S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + 3'-O-methyltricetin
S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + 3'-O-methyltricetin
S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
Substrates: the enzyme catalyzes three sequential O-methylations, forming 3'-O-methyltricetin, 3',5'-dimethyltricetin and 3',4',5'-O-trimethyltricetin. Tricetin is the preferred substrate
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S-adenosyl-L-methionine + 3'-O-methyltricetin
S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: i.e. 5,7,3',4',5'-pentahydroxyflavone, most preferred substrate
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3'-O-methyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3'-O-methyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3'-O-methyltricetin
Substrates: the enzyme catalyzes three sequential O-methylations, forming 3'-O-methyltricetin, 3',5'-dimethyltricetin and 3',4',5'-O-trimethyltricetin. Tricetin is the preferred substrate
Products: -
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3'-O-methyltricetin
Substrates: -
Products: -
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additional information
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Substrates: stepwise methylation of tricetin involving deprotonation of its hydroxyl groups by a His262-Asp263 pair followed by nucleophilic attack of SAM-methyl groups, substrate binding is mediated by an extensive network of H-bonds and van der Waals interactions, residue Val309 determines substrate specificity for tricetin and may define the evolutionary differences between the two closely related proteins, COMT and flavone OMT, molecular modeling, overview
Products: -
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additional information
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Substrates: stepwise methylation of tricetin involving deprotonation of its hydroxyl groups by a His262-Asp263 pair followed by nucleophilic attack of SAM-methyl groups, substrate binding is mediated by an extensive network of H-bonds and van der Waals interactions, residue Val309 determines substrate specificity for tricetin and may define the evolutionary differences between the two closely related proteins, COMT and flavone OMT, molecular modeling, overview
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additional information
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Substrates: structure-function relationships, homology modeling and molecular docking using MsCOMT crystal structure, PDB ID 1KYZ, overview
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additional information
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Substrates: structure-function relationships, homology modeling and molecular docking using MsCOMT crystal structure, PDB ID 1KYZ, overview
Products: -
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S-adenosyl-L-methionine + 3',5'-O-dimethyltricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + 3'-O-methyltricetin
S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
Substrates: -
Products: -
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3',4',5'-O-trimethyltricetin
Substrates: i.e. 5,7,3',4',5'-pentahydroxyflavone, most preferred substrate
Products: -
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S-adenosyl-L-methionine + tricetin
S-adenosyl-L-homocysteine + 3'-O-methyltricetin
Substrates: -
Products: -
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additional information
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additional information
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Substrates: stepwise methylation of tricetin involving deprotonation of its hydroxyl groups by a His262-Asp263 pair followed by nucleophilic attack of SAM-methyl groups, substrate binding is mediated by an extensive network of H-bonds and van der Waals interactions, residue Val309 determines substrate specificity for tricetin and may define the evolutionary differences between the two closely related proteins, COMT and flavone OMT, molecular modeling, overview
Products: -
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additional information
?
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Substrates: stepwise methylation of tricetin involving deprotonation of its hydroxyl groups by a His262-Asp263 pair followed by nucleophilic attack of SAM-methyl groups, substrate binding is mediated by an extensive network of H-bonds and van der Waals interactions, residue Val309 determines substrate specificity for tricetin and may define the evolutionary differences between the two closely related proteins, COMT and flavone OMT, molecular modeling, overview
Products: -
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D263E
site-directed mutagenesis, severe loss of activity is due to a conflict between the catalytic His262-imidazole group and Glu-CH2
D263E
severe loss of activity is due to a conflict between the catalytic His262-imidazole group and Glu-CH2
D263I
site-directed mutagenesis, Ile263 can not form a H-bond with 3'-OH group, the mutant shows almost complete loss in activity
D263I
no activity, Ile263 can not form a H-bond with 3'-OH group
D263N
site-directed mutagenesis, slight decrease in activity due to a decreased electronegativity of Asn-N compared to Asp-O, that affects charge transfer to tricetin-OH groups
D263N
slight decrease in activity due to a decreased electronegativity of Asn-N compared to Asp-O, that affects charge transfer to tricetin-OH groups
E290I
site-directed mutagenesis, almost complete loss of activity is due to the fact that Ile can not form a H-bond with the 4'-OH of tricetin
E290I
loss of activity is due to the fact that Ile can not form a H-bond with the 4'-OH of tricetin
E290Q
site-directed mutagenesis, the mutation results in a more extensive H-bonding that hinders charge transfer and affects B-ring flexibility and almost complete loss in activity
E290Q
no activity. This mutation results in a more extensive H-bonding that hinders charge transfer and affects B-ring flexibility
E322I
site-directed mutagenesis, loss of charge or a change in the side chain affects H-bonding with the neighboring residues, especially His262, the mutant shows reduced activity and altered kinetics compared to the wild-type enzyme
E322I
Km increased compared to wild-type, kcat/Km decreased compared to wild-type. Loss of charge or a change in the side chain affects H-bonding with the neighboring residues, especially His262
E322Q
site-directed mutagenesis, the mutant shows reduced activity compared to the wild-type enzyme
G305A
site-directed mutagenesis, the mutant shows reduced activity compared to the wild-type enzyme, the mutation results in loss of activity due to loss of H-bonding with the amide group of the neighboring Asn348
G305A
Loss of activity due to loss of H-bonding with the amide group of the neighboring Asn348
G305S
site-directed mutagenesis, change in polarity is less effective than chain length on catalytic activity
G305S
Km increased compared to wild-type, kcat/Km decreased compared to wild-type. Change in polarity is less effective than chain length on catalytic activity
H262F
site-directed mutagenesis, the mutant shows highly reduced activity compared to the wild-type enzyme
H262L
site-directed mutagenesis, the mutant shows highly reduced activity compared to the wild-type enzyme
H262R
site-directed mutagenesis, the mutant shows highly reduced activity compared to the wild-type enzyme, the mutation results in almost complete loss of protein expression, all mutant proteins lack imidazole ring that is critical for proton flow among His262, Asp263 and the substrate
H262R
results in almost complete loss of protein expression. All mutant proteins lack imidazole ring that is critical for proton flow among His262, Asp263 and the substrate
N124I
site-directed mutagenesis, the mutant shows highly reduced activity compared to the wild-type enzyme, the mutation results in a decreased substrate binding but not protein folding. Both mutations disrupt H-bonding with 5-OH group of tricetin
N124I
no activity. Mutation results in a decreased substrate binding but not protein folding. Mutations disrupt H-bonding with 5-OH group of tricetin
N124Q
site-directed mutagenesis, the mutant shows highly reduced activity compared to the wild-type enzyme
N124Q
no activity. Mutation results in a decreased substrate binding but not protein folding. Mutations disrupt H-bonding with 5-OH group of tricetin
W259A
site-directed mutagenesis, the mutant shows reduced activity compared to the wild-type enzyme, Ala can maintain the H-bonding network between Trp259, Glu290 and His262, wheras Tyr cannot
W259A
Km increased compared to wild-type, kcat/Km decreased compared to wild-type. Ala can maintain the H-bonding network between Trp259, Glu290 and His262, wheras Tyr cannot
W259Y
site-directed mutagenesis, the mutant shows reduced activity compared to the wild-type enzyme
W259Y
Km increased compared to wild-type, kcat/Km decreased compared to wild-type
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Zhou, J.M.; Gold, N.D.; Martin, V.J.; Wollenweber, E.; Ibrahim, R.K.
Sequential O-methylation of tricetin by a single gene product in wheat
Biochim. Biophys. Acta
1760
1115-1124
2006
Triticum aestivum (Q38J50), Triticum aestivum
brenda
Kornblatt, J.A.; Zhou, J.M.; Ibrahim, R.K.
Structure-activity relationships of wheat flavone O-methyltransferase: a homodimer of convenience
FEBS J.
275
2255-2266
2008
Triticum aestivum (Q38J50)
brenda
Zhou, J.M.; Seo, Y.W.; Ibrahim, R.K.
Biochemical characterization of a putative wheat caffeic acid O-methyltransferase
Plant Physiol. Biochem.
47
322-326
2008
Triticum aestivum (Q84N28), Triticum aestivum
brenda
Zhou, J.M.; Lee, E.; Kanapathy-Sinnaiaha, F.; Park, Y.; Kornblatt, J.A.; Lim, Y.; Ibrahim, R.K.
Structure-function relationships of wheat flavone O-methyltransferase: homology modeling and site-directed mutagenesis
BMC Plant Biol.
10
156
2010
Triticum aestivum (Q38J50), Triticum aestivum
brenda
Moheb, A.; Agharbaoui, Z.; Kanapathy, F.; Ibrahim, R.K.; Roy, R.; Sarhan, F.
Tricin biosynthesis during growth of wheat under different abiotic stresses
Plant Sci.
201-202
115-120
2013
Triticum aestivum (Q38J50), Triticum aestivum
brenda
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