Homo sapiens Reaction:

Superclasses: Reactions Classified By Conversion TypeSimple ReactionsChemical Reactions
Reactions Classified By SubstrateSmall-Molecule Reactions

EC Number:

Enzymes and Genes:
catechol O-methyltransferase: COMT
transmembrane O-methyltransferase: LRTOMT

In Pathway: dopamine degradation

Note that this reaction equation differs from the official Enzyme Commission reaction equation for this EC number, which can be found here .

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction in which it was curated.

Most BioCyc compounds have been protonated to a reference pH value of 7.3. Please see the PGDB Concepts Guide for more information.

Mass balance status: Balanced.

Direct generic reaction:
a catechol + S-adenosyl-L-methionine → a guaiacol + S-adenosyl-L-homocysteine + H+ (

Enzyme Commission Primary Name: catechol O-methyltransferase

Enzyme Commission Synonyms: COMT I , COMT II, S-COMT (soluble form of catechol-O-methyltransferase), MB-COMT (membrane-bound form of catechol-O-methyltransferase), catechol methyltransferase, catecholamine O-methyltransferase

Enzyme Commission Summary:
The mammalian enzyme acts more rapidly on catecholamines such as adrenaline or noradrenaline than on catechols.

Citations: [AXELROD58, Gulliver79, Huh79]

Gene-Reaction Schematic

Gene-Reaction Schematic

Instance reactions of [a catechol + S-adenosyl-L-methionine → a guaiacol + S-adenosyl-L-homocysteine + H+] (
i1: (R)-noradrenaline + S-adenosyl-L-methionine → normetanephrine + S-adenosyl-L-homocysteine + H+ (

i2: S-adenosyl-L-methionine + dopamine → S-adenosyl-L-homocysteine + 3-methoxytyramine + H+ (

i3: 3,4-dihydroxymandelate + S-adenosyl-L-methionine → vanillyl mandelate + S-adenosyl-L-homocysteine + H+ (

i4: 3,4-dihydroxyphenylacetate + S-adenosyl-L-methionine → homovanillate + S-adenosyl-L-homocysteine + H+ (
i5: (R)-adrenaline + S-adenosyl-L-methionine → metanephrine + S-adenosyl-L-homocysteine + H+ (

i6: 3,4-dihydroxyphenylglycol + S-adenosyl-L-methionine → 3-methoxy-4-hydroxyphenylglycol + S-adenosyl-L-homocysteine + H+ (

i7: L-dopa + S-adenosyl-L-methionine → 3-O-methyldopa + S-adenosyl-L-homocysteine + H+ (

Relationship Links: BRENDA:EC:, ENZYME:EC:, IUBMB-ExplorEnz:EC:


AXELROD58: AXELROD J, TOMCHICK R (1958). "Enzymatic O-methylation of epinephrine and other catechols." J Biol Chem 233(3);702-5. PMID: 13575440

Gulliver79: Gulliver PA, Tipton KF (1979). "The purification and properties of pig brain catechol-o-methyltransferase." J Neurochem 32(5);1525-9. PMID: 438821

Huh79: Huh MM, Friedhoff AJ (1979). "Multiple molecular forms of catechol-O-methyltransferase. Evidence for two distinct forms, and their purification and physical characterization." J Biol Chem 254(2);299-308. PMID: 762061

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Please cite the following article in publications resulting from the use of HumanCyc: Genome Biology 6(1):1-17 2004
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