Studies of Human Ceruloplasmin Fractions Separated by Chromatography on Hydroxylapatite.

Recent physicochemical(l,2) and immunochemical(3) studies from our laboratory have shown that human ceruloplasmin is a labile protein the properties of which are readily modified by a variety of experimental conditions. Our previous data, however, indicated that crystalline ceruloplasmin was a single protein. This is at variance with results from other laboratories which have shown that chromatography on hydroxylapatite columns resolves two discrete ceruloplasmins (4, 5). Curzon and Vallet (6) have also noticed small amounts of ceruloplasmin eluting from diethylaminoethyl cellulose after the main peak. Through use of a combination of diethylaminoethyl cellulose and hydroxylapatite chromatographic procedures, Morel1 and Scheinberg (7) have indicated that at least four different ceruloplasmins could be resolved. When crystalline ceruloplasmin (8, 9) is chromatographed on hydroxylapatite columns, a series of components are separated. Two of these, which appear to be analogous to the oxidase-active components first recognized by Broman (4), comprise the major portion of the protein. They have been subjected to various physicochemical and immunological studies, and the results are reported here.