ABSTRACT
Iron is required in almost all organisms for growth and crucial metabolic pathways. The redox properties of iron favor its use in a large number of protein complexes. Some require iron in the form of heme (Chapter 9) or iron-sulfur clusters (Chapter 10), but other forms are also known (Chapter 11). The major functions of iron are in electron transfer reactions, oxygen transport, and a variety of catalytic processes. Although iron is an essential element, excess iron is hazardous because it produces free oxygen radicals that damage DNA, proteins, and lipids. In humans, accumulation of cellular iron can result in cirrhosis, arthritis, heart failure, diabetes mellitus, and increased risk of cancer. Several diseases, such as anemia and hemochromatosis, are correlated with iron overload and deficiency disorders ([1] and references therein). Therefore, the maintenance of iron homeostasis in the body as well as in the cells must be balanced to supply enough iron for the metabolism and to avoid excessive, toxic levels. This occurs primarily by regulation of iron absorption; excretion has a more passive role.
