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Catalytic Site Atlas Version 2.2.12
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CSA entry for 1kyw
Original Entry
Title:
Transferase
Compound:
Caffeic acid 3-o-methyltransferase
Mutant:
No
UniProt/Swiss-Prot:
P28002-COMT_MEDSA
EC Class:
2.1.1.68
Other CSA Entries:
Overview of all sites for 1kyw
Homologues of 1kyw
Entries for UniProt/Swiss-Prot: P28002
Entries for EC: 2.1.1.68
Other Databases:
PDB entry: 1kyw
PDBsum entry: 1kyw
UniProt/Swiss-Prot: P28002
IntEnz entry: 2.1.1.68
Literature Report:
Introduction:
COMT is involved in lignin biosynthesis - it methylates caffeoyl- and 5-hydroxyferuloyl-containing acids, aldehydes and alcohols.

Lignin polymerisation has implications in industrial, environmental and agricultural areas.
Mechanism:
COMT is an S-adenosyl-L-Met-dependent methyltransferase that methylates 3'-hydroxyl- and 5'-hydroxyl-containing phenylpropanoid-derived lignin precursors.

Using His 269 as a general base, the 3'- or 5'-hydroxyl group is deprotonated, facilitating the transfer of the reactive methyl group of S-adenosyl-L-Met to the phenolate anion by nucleophilic attack.
Sites:

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Found by:
Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
HISA 269 269Sidechain
Acid/baseSubstrate
Functions as a general base to deprotonate the hydroxyl group and increase the nucleophilicity of the oxygen.
Evidence from paper Evidence concerns Evidence type
PubMed ID 12084826 Current protein Mutagenesis of residue
PubMed ID 12084826 Current protein Structural similarity to homologue of known mechanism
PubMed ID 11224575 Related protein: UniProt P93324 Structural similarity to homologue of known mechanism
PubMed ID 11224575 Related protein: O24529 Residue is positioned appropriately (ligand position known)
PubMed ID 11224575 Related protein: UniProt P93324 Residue is positioned appropriately (ligand position known)
PubMed ID 12084826 Current protein Conservation of residue
PubMed ID 12084826 Current protein Residue is positioned appropriately (ligand position known)
PubMed ID 11224575 Related protein: O24529 Mutagenesis of residue
PubMed ID 11224575 Related protein: O24529 Structural similarity to homologue of known mechanism
PubMed ID 11224575 Related protein: UniProt P93324 Mutagenesis of residue
References:
1
Structural basis for the modulation of lignin monomer methylation by caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferase.
C. Zubieta and P. Kota and J. L. Ferrer and R. A. Dixon and J. P. Noel
Plant Cell 14, (6) 1265-77, (2002).
12084826
2
Structures of two natural product methyltransferases reveal the basis for substrate specificity in plant O-methyltransferases.
C. Zubieta and X. Z. He and R. A. Dixon and J. P. Noel
Nat Struct Biol 8, (3) 271-9, (2001).
11224575
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