Reduction of mammalian ferritin.

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Abstract
Mammalian ferritin from horse spleen undergoes an electrochemical or chemical reduction reaction in which each iron atom present is reduced by 1 electron (2300 electrons/ferritin molecule containing 2300 Fe3+ ions). Midpoint potentials of -190 mV, -310 mV and -416 mV were determined at pH 7.0, 8.0 and 9.0. This variation of potential with pH indicates that .apprxeq. 2 H+ are transferred to the core for each Fe3+ reduced to Fe2+. Mossbauer measurements of partially reduced ferritin give spectra that consist of a ferric quadrupole doublet with a superposed ferrous quadrupole doublet. The relative intensities of these doublets are consistent with the electrochemically determined degree of reduction.