THE COUPLED REDOX POTENTIAL OF THE LACTATE-ENZYME-PYRUVATE SYSTEM

1. The term "coupled redox potential" is defined.

2. The system lactic ion

See PDF for Equation

pyruvic ion + 2H⁺ + 2e is shown

to be reversible (when the enzyme is lactic acid dehydrogenase) and its coupled redox potential between pH 5.2 and 7.2 at 32°C. is:

See PDF for Equation

3. The free energy of the reaction:

lactic ion (1m) → pyruvic ion (1m) = -ΔF = –14,572.

4. The standard free energy of formation (ΔF₂₉₈) of pyruvic acid (l) is estimated at –108,127. This is merely an approximation as some necessary data are lacking.

5. The importance of coupled redox potentials as a factor in the regulation of the equilibrium of metabolites is indicated.