The selective immobilization of ceruloplasmin onto the chromatographic material used for its purification

Summary When mammalian plasma was passed through a chromatographic material containing aminoethyl functional groups, ceruloplasmin was selectively retained. At a specific ionic strength of the eluant buffer, a single chromatographic peak corresponding to the electrophoretically homogeneous purified ceruloplasmin was eluted. This single-step procedure is easy to perform and gave a purification yield of more than 60%. The direct immobilization of the ceruloplasmin, while it was still adsorbed and concentrated at the basal part of the gel bed (last stage of the purification), was achieved by carbodiimide treatment, with coupling yields of 50–70%.The immobilized ceruloplasmin retained about 100% of its enzymatic activity. Kinetic studies have shown a decreased affinity of the immobilized protein for the substrate and a maximal velocity of 81% as compared to the free protein. The immobilized ceruloplasmin was much more resistant to proteolytic attack than the free enzyme which is highly protease sensitive. Using pronase and thermolysine proteases, the activity of free ceruloplasmin was entirely lost in few hours. However, under similar conditions, the immobilized ceruloplasmin exhibited a high stability, maintaining its integral activity even after 24 hours of proteolytic attack.