Haptoglobin is a glycoprotein secreted in the blood plasma that binds free haemoglobin thereby inhibiting its oxidative activity and preventing iron loss following haemolysis. Haptoglobin also regulates the activity of many cell types of the immune system and is an extracellular chaperone. Haptoglobin is produced mostly by hepatocytes but also by other tissues: e.g. skin, lung and kidney. Haptoglobin is a tetramer of two alpha- and two beta-chains, connected by disulfide bridges. The chains originate from a common precursor protein, which is proteolytically cleaved during protein synthesis.
