Purification and properties of human serum dopamine-β -hydroxylase

✍ Scribed by Takeyuki Ikeno; Seiichi Hashimoto; Hiroshi Kuzuya; Toshiharu Nagatsu

• Publisher: Springer
• Year: 1977
• Tongue: English
• Weight: 519 KB
• Volume: 18
• Category: Article
• ISSN: 0300-8177
• DOI: 10.1007/bf00280277

✦ Synopsis

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.