Binding of Iron to Amino Acids and Serum Proteins in Vitro 1

Summary

Following incubation of ⁵⁹Fe with pooled native human serum in vitro, ultrafiltrable iron was determined to be 5 to 7.5% of the total serum iron, at different levels of iron:albumin molar ratios. Under similar conditions approximately 2% of iron was ultrafiltrable when predialyzed serum was used. In physiological concentrations, additions of amino acids to predialyzed serum increased ultrafiltrable ⁵⁹Fe to similar levels as that observed for native human serum. Histidine and lysine showed significant effects in this regard. Amino acids competed effectively with albumin and only to a lesser degree with transferrin for binding of iron, suggesting a tighter affinity of iron for transferrin.