title: Purification and properties of human serum dopamine-beta-hydroxylase.
abstract: 1. Two different molecular forms of dopamine-beta-hydroxylase were isolated from human serum; a major component (Peak I enzyme) with a molecular weight of 368000 and with a higher specific activity and a minor component (Peak II enzyme) with a molecular weight of 188000 and with a lower specific activity. 2. Both forms require ascorbic acid for the activity, and are stimulated by fumarate. Addition of N-ethylmaleimide or copper also increased the activity. The optimal pH of both forms in the presence of 20mM tyramine as substrate is 5.0. 3. Km values toward tyramine of Peak I enzyme and Peak II enzyme were 1.67 mM and 14.2 mM respectively. 4. Both Peak I enzyme and Peak II enzyme are glycoprotein.
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D002417:Cattle; D003300:Copper / Q000494:pharmacology; D004299:Dopamine beta-Hydroxylase / Q000097:blood* / Q000302:isolation & purification; D005033:Ethylmaleimide / Q000494:pharmacology; D005650:Fumarates / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000097:blood* / Q000302:isolation & purification; D008970:Molecular Weight; D013045:Species Specificity; D014439:Tyramine / Q000378:metabolism
chemical_list: D005650:Fumarates; D007527:Isoenzymes; D003300:Copper; D004299:Dopamine beta-Hydroxylase; D005033:Ethylmaleimide; D001205:Ascorbic Acid; D014439:Tyramine