The biological role of ceruloplasmin and its oxidase activity.

Ceruloplasmin (ferroxidase) the blue Cu-protein of vertebrate plasma, possesses significant oxidase activity towards Fe(II) and numerous aromatic amines and phenols. Its ferroxidase activity has led to the discovery that it is a molecular link between copper and iron metabolism. Ceruloplasmin mobilizes iron into the plasma from iron storage cells in the liver. An additional role of Cp may be as a contributor to the regulation of the balance of biogenic amines through its oxidase action on the epinephrine and the hydroxyindole series. Ceruloplasmin also serves as a major copper transport vehicle, comparable to transferrin for iron. Evidence is presented that the copper atoms of Cp are a prerequisite for copper utilization in the biosynthesis of cytochrome oxidase. The ability of Cp to release copper at specific cellular sites is believed to be related to its broad substrate spectrum of biological reducing agents. Thus Cp is a serum protein with several important functions, all of which are directly related to its oxidase activity.