Oyarce A M, Fleming P J
Department of Biochemistry, Georgetown University Medical Center, Washington, DC 20007.
J Mol Neurosci. 1989;1(3):171-5. doi: 10.1007/BF02918903.
Dopamine beta-hydroxylase exists as soluble and membrane-bound forms in secretory vesicles. The soluble form of the enzyme contains identical subunits of 72 kDa and the membrane-bound form contains two non-identical subunits of 72 kDa and 75 kDa. The difference in the banding pattern on sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggests the presence of either an extra peptide, or membrane-binding segment, or differential glycosylation of 75-kDa subunits of the membranous form. Soluble and membranous forms of the enzyme were deglycosylated with endoglycosidases to elucidate the contribution of the carbohydrate moieties to the banding pattern on a sodium dodecyl sulfate-polyacrylamide gel. The deglycosylated species of both forms appeared to be identical and showed a decrease in apparent molecular weights to 66 kDa. These results indicate that the banding pattern of soluble and membranous dopamine beta-hydroxylase on sodium dodecyl sulfate-polyacrylamide gel electrophoresis may not be due to a membrane-binding anchor but rather to carbohydrate moieties.
多巴胺β-羟化酶以可溶性和膜结合形式存在于分泌小泡中。该酶的可溶性形式包含72 kDa的相同亚基，而膜结合形式包含72 kDa和75 kDa的两个不同亚基。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳上条带模式的差异表明，膜结合形式的75 kDa亚基存在额外的肽段、膜结合区段或不同的糖基化。用内切糖苷酶对该酶的可溶性和膜结合形式进行去糖基化处理，以阐明碳水化合物部分对十二烷基硫酸钠-聚丙烯酰胺凝胶上条带模式的影响。两种形式的去糖基化产物似乎相同，且表观分子量降至66 kDa。这些结果表明，可溶性和膜结合型多巴胺β-羟化酶在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳上的条带模式可能不是由于膜结合锚定，而是由于碳水化合物部分。
