Dopamine β-hydroxylase (DβH; also dopamine β-monooxygenase) is a 73 - 77 kDa member of the copper type II ascorbate-dependent monooxygenase family. It is both soluble (73 kDa) and membrane-bound (77 kDa) (anchored by an uncleaved signal sequence), and via hydroxylation, converts dopamine into norepinepherine.
Human DβH is a copper-containing disulfide-linked homodimer that is found in neurons and adrenal medullary cells. It is 603 amino acids (aa) in length and contains a 25 aa signal sequence followed by three domains. The first is an N-terminal 120 aa DOMON domain (dopamine β-monooxygenase N-terminal) that may either bind DβH to the cell membrane, or participate in tetramerization. This is followed by two 150 aa Cu+-type II ascorbate-dependent monooxygenase domains (aa 182 - 330 and 352 - 512). DβH may be most active as a dimeric-dimer/tetramer, whose association status is dependent on local Cl- concentrations.