Reversibility in Biological Oxidations

Author: Schott, Hermann Franz

Year: 1933

Degree: Dissertation (Ph.D.)

Advisor: Unknown, Unknown

Committee Member: Unknown, Unknown

Option: Biology

DOI: 10.7907/XKVV-TR72

Abstract

I. The molal electrode potential for the succinate-enzyme- fumarate equilibrium was determined for a series of variations of all the constituents, at 25°.

The free energy and the heat of the reaction, determined electrometrically, are compared to the values calculated from known physico-chemical properties of succinic and fumaric acids. The values agree within the limits of experimental error. This, together with the lack of dependence of the free energy on the source of the enzyme, is taken to indicate that the enzyme behaves as a perfect catalyst.

II. From the equilibrium constant for the reaction of fumarate and water to form 1-malate in the presence of the enzyme fumarase, the free energy of the reaction was calculated. From this value and the known physico-chemical properties of fumaric acid, the free energy of the formation of 1-malic acid was estimated.

III. It was demonstrated that in the presence of toluene-treated B. coli, lactate is oxidized to pyruvate, and that furthermore, pyruvate may also be reduced to lactate.

IV. It was shown that in the presence of toluene-treated B. coli electron or hydrogen transfer from one metabolite to another occurs only thru the mediation of a reversible oxidizing agent.

V. The implications of these findings for the theory of biological oxidations are discussed.

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