Importance of the aromatic ring in adrenergic amines. Nonaromatic analoques of phenylethanolamine as substrates for phenylethanolamine N-methyltransferase
Grunewald, G.L.; Grindel, J.M.; Vincek, W.C.; Borchardt, R.T.
Molecular Pharmacology 11(5): 694-699
ISSN/ISBN: 0026-895X PMID: 1237082 Accession: 068542713
Various nonaromatic analogs of phenylethanolamine were evaluated as substrates for phenylethanolamine N-methyltransferase (EC 2.1.1). The nonaromatic analogs were as good as, if not better than, phenylethanolamine itself as substrates for this enzyme. Evidence that these compounds were being N-methylated by EC 2.1.1 was obtained by isolating and identifying the N-methylated products. Competitive experiments using phenylethanolamine also provided evidence that EC 2.1.1 was the enzyme carrying out this methylation. The role of the aromatic ring of phenylethanolamine in binding to this enzyme would be due to its hydrophobic character, rather than its electron-rich nature. The data were inconsistent with the possibility of a charge-transfer complex being formed during the binding of phenylethanolamine to EC 2.1.1, but the existence of a hydrophobic binding site on the enzyme for this portion of the substrate molecule was suggested.