ceruloplasminhephaestin

Ceruloplasmin is a blue copper-containing glycoprotein primarily produced by the liver. It is the major copper-carrying protein in the bloodstream, binding the majority of circulating copper. The protein is encoded by the CP gene on chromosome 3 and is secreted into plasma as holo-ceruloplasmin, containing about six copper atoms per molecule; a portion exists as apoceruloplasmin, lacking copper.

Ceruloplasmin has ferroxidase activity, catalyzing the oxidation of ferrous (Fe2+) to ferric (Fe3+) iron. This oxidation is necessary for iron to bind to transferrin and to be exported from cells via ferroportin, contributing to systemic iron homeostasis. The protein also participates in antioxidant defense through its redox activity and functions as part of copper transport.

Clinically, ceruloplasmin levels in plasma are used as biomarkers in certain disorders. It is an acute-phase reactant, increasing in inflammation and infection. Low plasma ceruloplasmin levels or reduced ferroxidase activity are characteristic of Wilson disease, though levels can be normal in some patients. Very low or absent ceruloplasmin occurs in aceruloplasminemia, a rare autosomal recessive disorder caused by CP gene mutations, with brain iron accumulation, diabetes, and retinal degeneration. Measurement can be performed by immunoassay of holo- or apo-ceruloplasmin or by enzymatic ferroxidase activity assays.

In summary, ceruloplasmin links copper metabolism with iron homeostasis and has clinical relevance as a diagnostic marker in hepatic, inflammatory, and neurodegenerative disorders.