X-Ray Crystallography of Catechol O-Methyltransferase: Perspectives for Target-Based Drug Development

doi:10.1016/S1054-3589(08)60756-5

Advances in Pharmacology

Volume 42, 1997, Pages 328-331

https://doi.org/10.1016/S1054-3589(08)60756-5 Get rights and content

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Catechol O-methyltransferase (COMT) plays a role in the metabolism of catecholamines and some other substances containing the catechol structure. COMT also inactivates L-dopa, which is used as a drug in the treatment of Parkinson's disease. COMT catalyzes the transfer of the methyl group from the coenzyme S-adenosyl-L-methionine (AdoMet) to one of the phenolic hydroxyl groups of a catechol or substituted catechols. The presence of magnesium ions is required for the catalysis. The reaction products are O-methylated catechol and S-adenosyl-L-homocysteine (AdoHcy). COMT occurs in two forms, soluble and membrane-bound, the latter having a 50 amino-acids-long membrane anchor region. The membrane-bound COMT has about 10 times lower Km value than soluble COMT, but at saturating substrate concentrations, the catalytic number of both enzyme forms is similar. At low concentrations, catecholamines are methylated more efficiently by membrane-bound COMT. The active site of COMT consists of the AdoMet-binding domain and the catalytic site. The catalytic site is formed by a few amino acids that are important for substrate binding and catalysis of the methylation reaction, and by the metal ion. The Mg²⁺ bound to the enzyme makes the hydroxyl groups of the catechol substrate more easily ionizable. In a vicinity of one hydroxyl from the bound substrate, there is a lysine residue, which accepts the proton of that moiety, and subsequently the methyl group is transferred from the AdoMet to the hydroxyl. The shallow groove in the active site of COMT allows the long side chains of inhibitors to reach the surface of the enzyme. The best inhibitors of COMT are nitrocatechols. Ionized molecules penetrate poorly the blood brain barrier. In clinical trials it has been shown that the beneficial effect on the L-dopa metabolism in the treatment of Parkinson's disease is reached with a peripheral COMT inhibitor such as entacapone.

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Cited by (11)

Unveiling the biopathway for the design of novel COMT inhibitors
2022, Drug Discovery Today
Citation Excerpt :
In this context, the identification of potential novel COMT inhibitor by using quantitative structure–activity relationships studies (QSAR) modeling, ligand-based virtual screening, similarity searching, and pharmacophore generation has also been performed.59. Vidgren and coworkers use computational tools to study the molecular interactions of potential inhibitors with the COMT catalytic site.62 The acidity of both catechol hydroxyl groups and the lipophilicity of the inhibitors side chains were demonstrated to have an important role in the binding affinity of the molecules, later confirmed with the determination of the first COMT crystal structure.45
Catechol-O-methyltransferase (COMT) is an enzyme responsible for the O-methylation of biologically active catechol-based molecules. It has been associated with several neurological disorders, especially Parkinson’s disease (PD), because of its involvement in catecholamine metabolism, and has been considered an important therapeutic target for central nervous system disorders. In this review, we summarize the biophysical, structural, and therapeutical relevance of COMT; the medicinal chemistry behind the development of COMT inhibitors and the application of computer-aided design to support the design of novel molecules; current methodologies for the biosynthesis, isolation, and purification of COMT; and revise existing bioanalytical approaches for the assessment of enzymatic activity in several biological matrices.
Functional and structural characterization of a cation-dependent O-methyltransferase from the cyanobacterium Synechocystis sp. strain PCC 6803
2008, Journal of Biological Chemistry
Citation Excerpt :
Interestingly, the dimeric structure of the OMT of L. interrogans (14), in which the N termini are domain-swapped, suggests that the N-terminal residues could switch from the active site of one monomer to the other, allowing for a wider variety of potential products as observed for PFOMT and SynOMT. The proposed monomeric cation-dependent mammalian COMTs lack any lysine residues in the N-terminal region (5). In contrast to hydroxycinnamic acids, flavonoids with para-methylated B-rings are observed throughout the plant kingdom (35), although methylation is sometimes performed by cation-independent enzymes with strict structural requirements.
The coding sequence of the cyanobacterium Synechocystis sp. strain PCC 6803 slr0095 gene was cloned and functionally expressed in Escherichia coli. The corresponding enzyme was classified as a cation- and S-adenosyl-l-methionine-dependent O-methyltransferase (SynOMT), consistent with considerable amino acid sequence identities to eukaryotic O-methyltransferases (OMTs). The substrate specificity of SynOMT was similar with those of plant and mammalian CCoAOMT-like proteins accepting a variety of hydroxycinnamic acids and flavonoids as substrates. In contrast to the known mammalian and plant enzymes, which exclusively methylate the meta-hydroxyl position of aromatic di- and trihydroxy systems, Syn-OMT also methylates the para-position of hydroxycinnamic acids like 5-hydroxyferulic and 3,4,5-trihydroxycinnamic acid, resulting in the formation of novel compounds. The x-ray structure of SynOMT indicates that the active site allows for two alternative orientations of the hydroxylated substrates in comparison to the active sites of animal and plant enzymes, consistent with the observed preferred para-methylation and position promiscuity. Lys³ close to the N terminus of the recombinant protein appears to play a key role in the activity of the enzyme. The possible implications of these results with respect to modifications of precursors of polymers like lignin are discussed.
Biochemical and Structural Analysis of Substrate Promiscuity in Plant Mg<sup>2+</sup>-Dependent O-Methyltransferases
2008, Journal of Molecular Biology
Plant S-adenosyl-l-methionine-dependent class I natural product O-methyltransferases (OMTs), related to animal catechol OMTs, are dependent on bivalent cations and strictly specific for the meta position of aromatic vicinal dihydroxy groups. While the primary activity of these class I enzymes is methylation of caffeoyl coenzyme A OMTs, a distinct subset is able to methylate a wider range of substrates, characterized by the promiscuous phenylpropanoid and flavonoid OMT. The observed broad substrate specificity resides in two regions: the N-terminus and a variable insertion loop near the C-terminus, which displays the lowest degree of sequence conservation between the two subfamilies. Structural and biochemical data, based on site-directed mutagenesis and domain exchange between the two enzyme types, present evidence that only small topological changes among otherwise highly conserved 3-D structures are sufficient to differentiate between an enzymatic generalist and an enzymatic specialist in plant natural product methylation.
Discovery of Small Molecules as Membrane-Bound Catechol-O-methyltransferase Inhibitors with Interest in Parkinson’s Disease: Pharmacophore Modeling, Molecular Docking and In Vitro Experimental Validation Studies
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l-3,4-dihydroxyphenylalanine (l-DOPA) modulates brain iron, dopaminergic neurodegeneration and motor dysfunction in iron overload and mutant alpha-synuclein mouse models of Parkinson's disease
2019, Journal of Neurochemistry

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X-Ray Crystallography of Catechol O-Methyltransferase: Perspectives for Target-Based Drug Development

Publisher Summary

Molecular cloning and characterization of rat liver catechol-O-methyltransferase

Gene

Crystal structure of catechol O-methyltransferase

Nature