Hemopexin (HPX) is a serum glycoprotein responsible for the transport of heme to tissues such as liver, by receptor-mediated endocytosis. HPX binds heme with the highest affinity of any known protein. HPX is generally expressed in liver and belongs to acute phase reactants, the synthesis of which is induced after inflammation. Its function is scavenging the heme released or lost by the turnover of heme proteins such as hemoglobin and thus protects the body from the oxidative damage that free heme can cause. In addition, HPX releases its bound ligand for internalisation upon interacting with a specific receptor situated on the surface of liver cells. This function of HPX is to preserve the body’s iron.
HPX levels in serum reflect how much heme is present in the blood. Therefore, low HPX levels indicates that there has been significant degradation of heme containing compounds. Low HPX levels are one of the diagnostic features of an intravascular hemolytic anemia.