Intracellular iron

Iron in the cell, either bound to transport proteins, in an intermediate state or as part of metalloenzymes required for cellular function.

Description
The iron metabolism of all cells, despite vast differences in their specific differentiation and function, is similar. After obtaining iron from extracellular transferrin, iron is destined for processing in the mitochondria, which are the site of heme synthesis for mitochondrial cytochromes, for extramitochondrial cytochromes (such as cytochrome P450) or for other heme-iron proteins, such as myoglobin or hemoglobin, for which most iron is destined in vertebrates. Moreover, iron is incorporated in nonheme iron enzymes, such as the iron-sulphur proteins of the mitochondrial electron transport, and iron-activated enzymes, such as ribonucleotide reductase and aconitase. Excess cellular iron is exported by the iron exporter ferroportin, required to maintain intracellular iron homeostasis. Iron homeostasis, the maintenance of stable systemic and intracellular iron levels is critical for survival. When iron absorption from the diet is insufficient to replenish lost iron, hemoglobin levels fall and anemia occurs. Conversely, iron excess is also deleterious, with uncomplexed iron catalyzing the production of reactive oxygen species, which cause cellular injury and cell death. In hereditary hemochromatoses and as a result of long-term blood transfusion (in thalassemia major) or long-term increased erythrocyte turnover (in thalassemia intermedia), excess iron absorption leads to iron deposits in liver, heart and other organs, with consequent organ damage and functional failure.