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 degrees C. is: See PDF for Equation 3. The free energy of the reaction: lactic ion (1m) --> pyruvic ion (1m) = -DeltaF = -14,572. 4. The standard free energy of formation (DeltaF(298)) 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.