Analysis Note

Protein determined by biuret

Biochem/physiol Actions

Ceruloplasmin (Cp), the principal carrier of copper in plasma, is thought to be involved in oxidative modification of lipoproteins and participate in the acute phase reaction to stress. Cp is an effective antioxidant for a variety of radicals and has a potent peroxidase activity to decompose hydrogen peroxide in the presence of reduced glutathione. It inhibits the peroxidase activity of myeloperoxidase in a concentration-dependent manner and shows selective binding to myeloperoxidase in vitro. This suggests that ceruloplasmin may participate in the clearance and inactivation of myeloperoxidase in vivo. At physiological (micromolar) concentrations it was found to inhibit relaxation of rabbit aorta induced by endothelium-dependent agonists like acetylcholine or ADP. However, it was found ineffective toward vasodilation due to direct stimulation of smooth muscle cells by nitroglycerin. Cp plays an essential role in iron homeostasis, regulating the efflux of iron from macrophages and the oxidation of Fe²⁺ to Fe³⁺. Cp deficiency leads to neurodegenerative disorders, possibly by starving neurons of iron.

Physical form

Pale blue powder containing sodium chloride and sodium acetate

Unit Definition

One unit will cause a ΔA₅₅₀ of 0.01 per min using N,N-dimethyl-p-phenylenediamine as substrate at pH 5.5 and 37 °C, in a 7 mL reaction volume.