Transferrin

Transferrin is a glycoprotein that controls the level of free iron in biological fluids. It binds iron very tightly but reversibly. Although iron bound to transferrin is less than 0.1% (4 mg) of the total body iron, it is the most important iron pool, with the highest rate of turnover (25 mg/24 h). Transferrin has a molecular weight of around 80 KDa and contains two specific high-affinity iron (Fe3+) binding sites. The affinity of transferrin for Fe3+ is extremely high but decreases progressively with decreasing pH below neutrality.

Function

When not bound to iron, transferrin is known as "apotransferrin" (see Apoenzyme). Transferrin is synthesized in the liver and consists of a polypeptide chain containing 679 amino acids. It is a glycoprotein that binds iron very tightly but reversibly. Transferrin is responsible for the transport of iron from sites of absorption and heme degradation to those of storage and utilization.

Clinical significance

Serum transferrin levels are tested for in a number of clinical scenarios. Transferrin is used as a means of transporting iron in the blood plasma. The transferrin protein is coded by the TF gene.

See also

• Iron metabolism
• Transferrin saturation
• Transferrin receptor

References

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