Iron incorporation into apoferritin. The role of apoferritin as a ferroxidase

• Published in: The Journal of biological chemistry Vol. 261; no. 28; pp. 13182 - 13185
• Main Authors: Bakker, G R, Boyer, R F
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 05.10.1986; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Apoferritins - metabolism; Binding Sites; Biological and medical sciences; Cell physiology; Ferric Compounds - metabolism; Ferritins - analogs & derivatives; Ferrous Compounds - metabolism; Fundamental and applied biological sciences. Psychology; Horses; Humans; Iron - metabolism; Kinetics; Membrane and intracellular transports; Molecular and cellular biology; Oxidoreductases - metabolism; Quaternary Ammonium Compounds - metabolism; Transferrin - metabolism; Incorporation; Enzymatic activity; Ferritin; Oxidase; Coeruloplasmin; Ion transport; Molecular interaction; Iron; Mechanism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)69288-9

Apoferritin catalyzes the oxidation of Fe(II) to Fe(III). Ferroxidase activity is assayed and characterized by coupling the oxidation with the binding of Fe(III) to transferrin. The initial rate of Fe(II) oxidation is dependent on apoferritin and initial Fe(II) concentration but independent of transferrin concentration. The ferroxidase activity is inhibited by Zn(II). Ferritins with varying loads of iron have the same ferroxidase activity level. It is suggested that the described oxidation process represents the initial step of iron deposition in apoferritin. Since transferrin can intercept Fe(III) before it is deposited in apoferritin, active sites for Fe(II) oxidation must be on or near the surface of apoferritin. This finding is contrary to the current view of apoferritin-catalyzed oxidation of Fe(II) which places active sites in the channels to the core or inside the central core.