Catecholamine metabolism in the brain by membrane-bound and soluble catechol-o-methyltransferase (COMT) estimated by enzyme kinetic values
A kinetic model was constructed to reevaluate the catecholamine metabolism in hypothetical brain homogenates. Earlier published kinetic values of recombinant membrane-bound (MB-) COMT and soluble (S-) COMT were combined with data suggesting that MB-COMT represents 70% and 30% of total COMT protein i...
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Published in | Medical hypotheses Vol. 57; no. 5; pp. 628 - 632 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
Kidlington
Elsevier Ltd
01.11.2001
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | A kinetic model was constructed to reevaluate the catecholamine metabolism in hypothetical brain homogenates. Earlier published kinetic values of recombinant membrane-bound (MB-) COMT and soluble (S-) COMT were combined with data suggesting that MB-COMT represents 70% and 30% of total COMT protein in human and rat brain, respectively. In the rat brain model L-DOPA and 3,4-dihydroxybenzoic acid were O-methylated mainly via S-COMT, while dopamine and noradrenaline, at low concentrations, were O-methylated slightly more by MB-COMT. In the human brain model dopamine and noradrenaline were metabolized primarily by MB-COMT. The ratio of meta (3-methoxy) over para (4-methoxy) product formation from 3,4-dihydroxybenzoic acid was higher for MB-COMT than S-COMT. It is suggested that MB-COMT clearly predominates the O-methylation of dopamine and noradrenaline also in vivo. Additionally, meta/para ratios could support the enrichment of either isoform of COMT in a homogenate sample. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0306-9877 1532-2777 |
DOI: | 10.1054/mehy.2001.1430 |