Studies on iron binding by free fatty acids.

The effect of various saturated and unsaturated fatty acids on iron binding and the translocation of this complex into the organic phase were studied. The amount of iron translocated into the organic phase depended on the affinity of the respective fatty acid to iron. It was seen that saturated and monounsaturated fatty acids translocated more iron compared to polyunsaturated fatty acids. Positional isomers of oleic acid were as effective as oleic acid in translocating iron. It appears that the free carboxyl group on the fatty acid is essential, as the methyl ester of the fatty acid failed to translocate iron. Effect of varying the concentration of fatty acid and iron on iron translocation suggested the requirement of 3 to 4 moles of fatty acid for 1 mole of iron binding. Divalent cations such as Ca2+ and Mg2+ or lipids such as cholesterol or triolein did not compete with fatty acids but there was reduced translocation when phosphate buffer or phospholipid was included in the incubation medium, suggesting that phosphate interferes with the formation of fatty acid-iron complex. Thus it seems that free fatty acids are capable of forming a complex with iron.