Caeruloplasmin: a multi-functional metalloprotein of vertebrate plasma

Ceruloplasmin is a blue copper protein found in the alpha 2-globulin fraction of vertebrate plasma. It is a single-chain glycoprotein of molecular weight 132 000. It contains six copper atoms per molecule, comprising three or possibly four different types of copper. Its many functions may be related to the heterogeneous nature of these six copper atoms and to the various catalytic activities which they provide. Caeruloplasmin resembles albumin and transferrin in that all three serum proteins are regarded primarily as transport proteins. However, each has numerous other action as important as this transport function. Caeruloplasmin directly mobilizes iron into the serum and provides the major molecular link between copper and iron metabolism; it is the most prominent serum antioxidant, preventing deleterious oxidation of polyenoic acids and other substrates; it scavenges superoxide radicals; it serves as an acute-phase reactant (an endogenous modulator) of the inflammatory response; finally, caeruloplasmin may regulate the serum concentration of the biogenic amines, adrenaline (epinephrine) and serotonin (5-HT).