Spectrofluorometric study of iron removal from bovine lactoferrin by ethylenediamminetetraacetic acid

The kinetics of iron removal from the two metal binding sites of the bovine lactoferrin by ethylenediaminetetraacetic acid (EDTA) was investigated at pH 7.5 and 33°C. Solutions were buffered at pH 7.5 by 0.15 M Tris-HCl. Pseudo first-order rate constants as a function of ligand concentration were measured for iron removal from diferric lactoferrin and from N- and C-terminal monoferric lactoferrin. Diferric lactoferrin showed simple saturation behavior while both the monoferric forms showed a two-term dependence of kobs on ligand concentration that signifies two pathways for iron removal under the conditions applied. Moreover, the results show that the N-terminal site is more labile towards iron removal by EDTA than the C-terminal site.