Ceruloplasmin is the major copper-carrying protein in the blood, and in addition plays a role in iron metabolism. It was first described in 1948.4 Another protein, hephaestin, is noted for its homology to ceruloplasmin, and also participates in iron and probably copper metabolism.
Ceruloplasmin is an enzyme (EC184.108.40.206) synthesized in the liver containing 6 atoms of copper in its structure.5 Ceruloplasmin carries more than 95% of the total copper in healthy human plasma.6 The rest is accounted for by macroglobulins. Ceruloplasmin exhibits a copper-dependent oxidase activity, which is associated with possible oxidation of Fe2+ (ferrous iron) into Fe3+ (ferric iron), therefore assisting in its transport in the plasma in association with transferrin, which can carry iron only in the ferric state. The molecular weight of human ceruloplasmin is reported to be 151kDa.
A cis-regulatory element called the GAIT element is involved in the selective translational silencing of the Ceruloplasmin transcript.7 The silencing requires binding of a cytosolic inhibitor complex called IFN-gamma-activated inhibitor of translation (GAIT) to the GAIT element.8
Like any other plasma protein, levels drop in patients with hepatic disease due to reduced synthesizing capabilities.
Copper availability doesn't affect the translation of the nascent protein. However, the apoenzyme without copper is unstable. Apoceruloplasmin is largely degraded intracellularly in the hepatocyte and the small amount that is released has a short circulation half life of 5 hours as compared to the 5.5 days for the holo-ceruloplasmin.
Mutations in the ceruloplasmin gene (CP), which are very rare, can lead to the genetic disease aceruloplasminemia, characterized by hyperferritinemia with iron overload. In the brain, this iron overload may lead to characteristic neurologic signs and symptoms, such as cerebellar ataxia, progressive dementia, and extrapyramidal signs. Excess iron may also deposit in the liver, pancreas, and retina, leading to cirrhosis, endocrine abnormalities, and loss of vision, respectively.
Lower-than-normal ceruloplasmin levels may indicate the following:
^Holmberg CG, Laurell C-B (1948). "Investigations in serum copper. II. Isolation of the Copper containing protein, and a description of its properties". Acta Chem Scand2: 550–56. doi:10.3891/acta.chem.scand.02-0550.
^Ziakas A, Gavrilidis S, Souliou E, Giannoglou G, Stiliadis I, Karvounis H, Efthimiadis G, Mochlas S, Vayona MA, Hatzitolios A, Savopoulos C, Pidonia I, Parharidis G (2009). "Ceruloplasmin is a better predictor of the long-term prognosis compared with fibrinogen, CRP, and IL-6 in patients with severe unstable angina". Angiology60 (1): 50–9. doi:10.1177/0003319708314249. PMID18388036.
Giurgea N, Constantinescu MI, Stanciu R, et al. (2005). "Ceruloplasmin - acute-phase reactant or endogenous antioxidant? The case of cardiovascular disease". Med. Sci. Monit.11 (2): RA48–51. PMID15668644.
Rask L, Valtersson C, Anundi H, et al. (1983). "Subcellular localization in normal and vitamin A-deficient rat liver of vitamin A serum transport proteins, albumin, ceruloplasmin and class I major histocompatibility antigens". Exp. Cell Res.143 (1): 91–102. doi:10.1016/0014-4827(83)90112-X. PMID6337857.
Kingston IB, Kingston BL, Putnam FW (1980). "Primary structure of a histidine-rich proteolytic fragment of human ceruloplasmin. I. Amino acid sequence of the cyanogen bromide peptides". J. Biol. Chem.255 (7): 2878–85. PMID6987229.