title: Non-reductive iron release from horse spleen ferritin using desferoxamine chelation.
abstract: The rate of Fe(3+) release from horse spleen ferritin (HoSF) was measured using the Fe(3+)-specific chelator desferoxamine (DES). The reaction consists of two kinetic phases. The first is a rapid non-linear reaction followed by a slower linear reaction. The overall two-phase reaction was resolved into three kinetic events: 1) a rapid first-order reaction in HoSF (k(1)); 2) a second slower first-order reaction in HoSF (k(2)); and 3) a zero-order slow reaction in HoSF (k(3)). The zero-order reaction was independent of DES concentration. The two first-order reactions had a near zero-order dependence on DES concentration and were independent of pH from 6.8 to 8.2. The two first-order reactions accounted for 6-9 rapidly reacting Fe(3+) ions. Activation energies of 10.5±0.8, 13.5±2.0 and 62.4±2.1kJ/mol were calculated for the kinetic events associated with k(1), k(2), and k(3), respectively. Iron release occurs by: 1) a slow zero-order rate-limiting reaction governed by k(3) and corresponding to the dissociation of Fe(3+) ions from the FeOOH core that bind to an Fe(3+) binding site designated as site 1 (proposed to be within the 3-fold channel); 2) transfer of Fe(3+) from site 1 to site 2 (a second binding site in the 3-fold channel) (k(2)); and 3) rapid iron loss from site 2 to DES (k(1)).
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Johnson
authors.forename: Jason
authors.initials: J
authors.lastname: Kenealey
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hilton
authors.forename: David
authors.initials: D
authors.lastname: Brosnahan
authors.forename: Richard K
authors.initials: RK
authors.lastname: Watt
authors.forename: Gerald D
authors.initials: GD
authors.lastname: Watt
mesh_terms: D000818:Animals; D002614:Chelating Agents / Q000737:chemistry*; D003676:Deferoxamine / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005293:Ferritins / Q000737:chemistry*; D006736:Horses; D007700:Kinetics; D010084:Oxidation-Reduction; D011485:Protein Binding; D013154:Spleen / Q000737:chemistry*; D013696:Temperature
chemical_list: D002614:Chelating Agents; D005290:Ferric Compounds; D005293:Ferritins; D003676:Deferoxamine