Determination of differential activities of soluble and membrane-bound catechol-O-methyltransferase in tissues and erythrocytes.
Catechol-O-methyltransferase (COMT) exists as two isoenzymes, a membrane-bound form (MB-COMT) and a soluble form (S-COMT), with different roles in the metabolism of catecholamines and other catechol compounds. This report documents an HPLC assay for separate estimation of S-COMT and MB-COMT activity and examines activities of the two isoenzymes among different rat tissues and in human and rat erythrocytes. Activities of MB-COMT and S-COMT varied widely among tissues. There were higher activities of S-COMT than MB-COMT in all tissues except the adrenal medulla where MB-COMT was the predominant isoenzyme, consistent with the importance of this tissue and MB-COMT for the O-methylation of catecholamines. MB-COMT and S-COMT in rat and human erythrocytes showed divergent levels and patterns of activity. The assay represents a rapid and accurate method for quantifying MB-COMT and S-COMT in various tissues and examining the relative roles of COMT isoenzymes in the metabolism of catechol compounds in health and disease.
Clinical Neuroscience Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
T
T
Ellingson
S
S
Duddempudi
B D
BD
Greenberg
D
D
Hooper
G
G
Eisenhofer
D000818:Animals; D002394:Catechol O-Methyltransferase / Q000097:blood / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000201:enzymology*; D006801:Humans; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012995:Solubility
D002394:Catechol O-Methyltransferase