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Xenobiotica. 2008 Feb;38(2):130-46. doi: 10.1080/00498250701744641 .

Molecular modelling study of the mechanism of high-potency inhibition of human catechol-O-methyltransferase by (-)-epigallocatechin-3-O-gallate.

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Department of Pharmacology, Toxicology and Therapeutics, School of Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA.


The molecular mechanism of inhibition of human catechol-O-methyltransferase (COMT) by (-)-epigallocatechin-3-O-gallate (EGCG), which is a modest substrate of COMT but an ultra-potent inhibitor of this enzyme, was studied. EGCG has an IC(50) value of 70 nM for inhibiting human liver COMT-mediated O-methylation of 2-hydroxyestradiol, which was 210-760 times more potent than catechin, epigallocatechin and epicatechin. Kinetic analyses showed that EGCG had a strong component of non-competitive inhibition of the O-methylation of 2-hydroxyestradiol. Computational molecular modelling studies showed that the B- and D-rings of EGCG can bind tightly to the human COMT in four different modes (i.e. D-para-OH, D-meta-OH, B-para-OH, and B-meta-OH). The binding geometry of EGCG in these binding modes was found to be less than ideal to form perfect Mg(2+) coordination for the catalysis of its own methylation. It is concluded that the very tight binding interaction of EGCG with COMT makes it a potent non-competitive inhibitor, but its imperfect geometry makes it a poor substrate for methylation by this enzyme.

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