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Hemozoin
Haemozoin is a disposal product formed from the digestion of blood by some blood-feeding parasites. These hematophagous organisms such as Malaria parasites (''Plasmodium spp.''), ''Rhodnius'' and ''Schistosoma'' digest haemoglobin and release high quantities of free heme, which is the non-protein component of hemoglobin. A heme is a prosthetic group that consists of an iron atom contained in the center of a heterocyclic porphyrin ring. Free heme is toxic to cells, so the parasites convert it into an insoluble crystalline form called hemozoin. In malaria parasites, hemozoin is often called ''malaria pigment''.
Since the formation of hemozoin is essential to the survival of these parasites, it is an attractive target for developing drugs and is much-studied in ''Plasmodium'' as a way to find drugs to treat malaria (malaria's Achilles' heel). Several currently used antimalarial drugs, such as chloroquine and mefloquine, are thought to kill malaria parasites by inhibiting haemozoin biocrystallization.
==Discovery==
Black-brown pigment was observed by Johann Heinrich Meckel in 1847, in the blood and spleen of a person suffering from insanity. However, it was not until 1849 that the presence of this pigment was connected to infection with malaria. Initially, it was thought that this pigment was produced by the body in response to infection, but Charles Louis Alphonse Laveran realized in 1880 that "malaria pigment" is, instead, produced by the parasites, as they multiplied within the red blood cell. The link between pigment and malaria parasites was used by Ronald Ross to identify the stages in the ''Plasmodium'' life cycle that occur within the mosquito, since, although these forms of the parasite are different in appearance to the blood stages, they still contain traces of pigment.
Later, in 1891, T. Carbone and W.H. Brown (1911) published papers linking the degradation of hemoglobin with the production of pigment, describing the malaria pigment as a form of hematin and disproving the widely held idea that it is related to melanin. Brown observed that all melanins were bleaching rapidly with potassium permanganate, while with this reagent malarial pigment manifests not the slightest sign of a true bleach reaction. The name "hemozoin" was proposed by Louis Westenra Sambon. In the 1930s several authors identified hemozoin as a pure crystalline form of α-hematin and showed that the substance did not contain proteins within the crystals,〔 but no explanation for the solubility differences between malaria pigment and α-hematin crystals was given.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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