I. The molal electrode potential for the succinate-enzyme-fumarate equilibrium was determined for a series ofvariations of all the constituents, at 25°.
The free energy and the heat of the reaction, determinedelectrometrically, are compared to the values calculatedfrom known physico-chemical properties of succinic and fumaricacids. The values agree within the limits of experimentalerror. This, together with the lack of dependence of thefree energy on the source of the enzyme, is taken to indicatethat the enzyme behaves as a perfect catalyst.
II. From the equilibrium constant for the reaction offumarate and water to form 1-malate in the presence of theenzyme fumarase, the free energy of the reaction was calculated.From this value and the known physico-chemical properties offumaric acid, the free energy of the formation of 1-malic acidwas estimated.
III. It was demonstrated that in the presence of toluene-treatedB. coli, lactate is oxidized to pyruvate, and thatfurthermore, pyruvate may also be reduced to lactate.
IV. It was shown that in the presence of toluene-treatedB. coli electron or hydrogen transfer from onemetabolite to another occurs only thru the mediation of areversible oxidizing agent.
V. The implications of these findings for the theoryof biological oxidations are discussed.
