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.
Ellingson
T
T
Clinical Neuroscience Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
Duddempudi
S
S
Greenberg
B D
BD
Hooper
D
D
Eisenhofer
G
G
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