Kinetic control of internal electron transfer in cytochrome c oxidase

Two alternative hypotheses have been proposed to account for the relatively slow (ms) internal eT observed in the oxidized cyt c oxidase. The thermodynamic control hypothesis states that eT between cyt a and a3 is very fast (μs), but the apparent reduction of cyt a3 is slow because thermodynamics favors reduced cyt a. Whereas the kinetic control hypothesis states that inter‐heme eT is intrinsically slow (ms), for the oxidized binuclear center.