[Structural study of dopamine beta hydroxylase purified from human serum].

Dopamine-beta-hydroxylase (DBH) has been purified from human serum. The ensyme appeared to be pure as judged by the criterion of polyacrylamide gel electrophoresis. The native protein has a molecular weight of 250,000. When treated with dithiothreitor, the native protein could be dissociated into species with molecular weight of 64,500 and 32,000. It is suggested that the human circulating DBH is composed of four subunits and that each subunit may be composed of two polypeptide chains.