Iron in Eukarya
Iron is essential for the normal physiological function of all organisms. In humans it is required for a plethora of biochemical roles including the transport of oxygen in the blood and energy production in the mitochondria. However, iron is also highly cytotoxic when present at high levels as it readily participates in oxidation-reduction reactions that lead to the generation of reactive oxygen species. One unique feature of iron biology is the lack of excretory mechanisms to remove excess iron from the body. Therefore, the concerted action of several genes and proteins working together to regulate the movement of iron across cell membranes, its storage in peripheral tissues and its physiological utilization in the body is essential for maintaining iron homeostasis. Humans are exposed to iron in a number of chemical forms (haem or non-haem; ferric or ferrous). This chapter will describe how humans acquire iron from their diet; the subsequent delivery of iron to its sites of utilization and storage; and how iron is recycled from effete erythrocytes for re-use in metabolism. Mutations in a number of the genes controlling iron metabolism have been identified and study of the pathological consequences of these mutations has allowed us to gain a greater understanding of how the body senses changes in iron status and coordinates its transport, storage and utilization to maintain homeostasis.