CAcT Home

Iron in Human

Iron is an essential elements for human. Ferritin, an iron-storage protein found in animals and plants, contains the largest cluster currently known, an ordered aggregate {(FeOOH)8(FeO H2PO4)}n containing up to 4,500 Fe(III) atoms. The cluster occurs within a protein cavity roughly 80 angstroms in diameter. Proteins in which heavy metal ions are bound directly to some of the side chains of histidine, cysteine, or some other amino acid are called metalloproteins. Two metalloproteins, transferrin and ceruloplasmin, occur in the globulin fractions of blood serum; they act as carriers of iron and copper, respectively. Transferrin has a molecular weight of 84,000 and consists of two identical subunits, each of which contains one ferric ion (Fe3+) that seems to be bound to tyrosine. Several genetic variants of transferrin are known to occur in man. Another iron protein, ferritin, which contains 20 to 22 percent iron, is the form in which iron is stored in animals; it has been obtained in crystalline form from liver and spleen. A molecule consisting of 20 subunits, its molecular weight is approximately 480,000. The iron can be removed by reduction from the ferric (Fe3+) to the ferrous (Fe2+) state. The iron-free protein, apoferritin, is synthesized in the body before the iron is incorporated.