Albertine Donker

Iron Function and Iron Handling from Fetus to Adult 53 2 IRON IS CRUCIAL FOR HUMAN LIFE The ability of iron to act as an electron receptor or electron donor forms the fundamental basis for its essential role in many biological processes; oxygen transport via the iron-containing heme component of hemoglobin, cellular respiration as part of heme-containing cytochromes and Fe/S cluster- containing proteins of the electron transport chain, DNA synthesis and cell growth, cell differentiation and regulation of gene expression. 1 In the human body, the great majority of body iron -approximately two-thirds- is dedicated to hemoglobin synthesis. 11 Body iron distribution and its function in the various compartments of the human body are summarized in Table 1 . For children, iron is especially essential for brain development. 1,12 Table 1. Distribution and function of iron in the human adult male body Compartment Iron content (mg) Key iron-containing protein(s) Function of iron- containing protein(s) Circulation 1,200-202 4 Transferrin Iron transport Erythropoietic system Erythroblasts in bone marrow 200-203 300 Hemoglobin Critical ligand for the binding and transport of O 2 Red blood cells in circulation 1,200-204 2500 Hemoglobin Critical ligand for the binding and transport of O 2 Circulating macrophages 200,202,205 600 Ferritin, hemosiderin Iron storage Muscular system 1,201 130 Myoglobin Critical ligand for the binding and transport of O 2 Central nervous system 1,12,206,207, ? Central nervous system oligodendrocytes Myelin synthesis Tryptophan hydroxylase Serotonin synthesis Tyrosine hydroxylase Norepinephrine and dopamine synthesis Monoamine oxydase Degradation of neurotransmitters Bone 62 ? Hydroxylases Production of collagen type I Cytochrome P450 Activation of vitamin D