Multiple forms of human dopamine beta-hydroxylase in SH-SY5Y neuroblastoma cells.
Dopamine beta-hydroxylase exists as three forms in human neuroblastoma (SH-SY5Y) cells. The membrane-bound form of the hydroxylase contains three different species with apparent relative molecular weights of 73,000, 77,000, and 82,000. The intracellular soluble form of dopamine beta-hydroxylase was present as a single species with an apparent molecular weight of 73,000. Pulse-chase experiments showed that membranous dopamine beta-hydroxylase contains two subunit forms of 73,000 and 77,000 after short chase times. The soluble hydroxylase was synthesized as a single species of 73,000 at approximately the same rate as the lower molecular weight species of the membranous enzyme. A constitutively secreted third form of the enzyme with an intermediate apparent molecular weight also incorporated [35S]sulfate, whereas no significant amount of [35S]sulfate was observed in the cellular forms of the enzyme. The [35S]sulfate was incorporated on N-linked oligosaccharides. Approximately 12% of the enzyme is released constitutively within 1 h. These results demonstrate that neuronal cells have the ability to constitutively secrete a specific form of dopamine beta-hydroxylase which may contribute to the levels of this enzyme found in plasma.
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, D.C. 20007.
A M
AM
Oyarce
P J
PJ
Fleming
D002460:Cell Line; D004299:Dopamine beta-Hydroxylase / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D008970:Molecular Weight; D009447:Neuroblastoma / Q000201:enzymology*; D011499:Protein Processing, Post-Translational; D012995:Solubility; D013347:Subcellular Fractions / Q000737:chemistry / Q000201:enzymology; D013431:Sulfates / Q000378:metabolism
D008565:Membrane Proteins; D013431:Sulfates; D004299:Dopamine beta-Hydroxylase