transferriniron
Transferriniron is the complex of iron ions bound to transferrin, a circulating plasma glycoprotein whose main function is to transport iron from sites of absorption and storage to cells that require it. Transferrin has two high-affinity iron-binding sites; each binds one Fe3+ ion in a coordinated fashion and typically requires a carbonate anion as a synergist. In its iron-loaded form, holo-transferrin circulates and delivers iron to most tissues via the transferrin receptor (TfR1) on the cell surface. The receptor binds holo-transferrin with high affinity at neutral pH and mediates receptor-mediated endocytosis. In the acidic endosome, iron is released, reduced from Fe3+ to Fe2+ by ferrireductases such as the STEAP family, and transported into the cytosol primarily by DMT1. The apotransferrin and TfR1 recycle to the cell surface, where apo-transferrin is released at neutral pH and can bind iron again.
Serum composition is described by transferrin concentration and transferrin saturation, the fraction of iron-binding sites occupied