Transferrin binding and PH

Transferrin binding to transferrin receptors reduces its affinity for iron. Two pathways can occur once endocytosed–degradation or recycling pathways. The degradation pathway is where the dissociation of ferric ions from transferrin occurs from an early and late endosome. Iron can now be utilized for storage or incorporated into hemoglobin. The recycling pathway involves the recycling of transferrin. After the dissociation of iron, transferrin is called apotransferrin. Apotransferrin remains bound to its receptor because it has a high affinity for its receptors at a reduced pH. It recycles back to the plasma membrane, still bound to its receptor. At a neutral pH, apotransferrin dissociates from its receptor to enter the circulation, reload iron, and repeat the cycle. All transferrin receptors eventually follow the degradation pathway for receptor turnover. An example of a cell is an erythroid precursor in the bone marrow. 

Ogun AS, Adeyinka A. Biochemistry, Transferrin. [Updated 2022 Nov 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532928/