Purification of membrane-bound dopamine β-monooxygenase from chromaffin granules: Relation to soluble dopamine β-monooxygenase

Membrane-bound dopamine β-monooxygenase (MDBH) has been solubilized using emulphogen, a nonionic detergent, and purified by a single-step anion-exchange chromatography on DEAE-cellulose. Reduced and denatured MDBH has a molecular weight of approximately 75,000. The unreduced MDBH has a molecular weight twice that size. MDBH and SDBH (soluble dopamine β-monooxygenase) possess many similar features. Using antiserum to SDBH, the two proteins show a reaction of identity in immunodiffusion assays. Their chromatographic, electrophoretic, and molecular weight characteristics are also very similar. Although the amino acid compositions of MDBH and SDBH were not dissimilar, the MDBH composition had a higher content of certain amino acids, particularly hydrophobic ones. Despite the remarkable likeness of MDBH and SDBH demonstrated above and by analytical peptide maps, peptides can be detected in MDBH which are not found in SDBH.