Apotransferrin

Transferrin is a glycoprotein that binds iron very tightly but reversibly. Although iron bound to transferrin is less than 0.1% (4mg) of the total body iron, it is the most important iron pool, with the highest rate of turnover (25mg/24 h). Transferrin has a molecular weight of around 80kD and contains 2 specific high-affinity Fe(III) binding sites. The affinity of transferrin for Fe(III) is extremely high but decreases progressively with decreasing pH below neutrality.