Biological oxidations in the succinic acid series

Abstract

THE oxidation of succinic acid can be accomplished by cells of very diverse types, ranging from the bacteria to those of mammalian muscle and brain. Early work on the course of this oxidation, by Batelli and Stern, Einbeck, and Dakin, showed that succinic acid was oxidised to fumaric acid and that this took up the elements of water to form l-malic acid. Hahn, Haarman and Fischbach [1929] demonstrated that in presence of muscle l-malic acid was further oxidised to oxaloacetic acid. In the case of bacteria it was clear The question, however, arose as to whether fumaric acid was oxidised directly or whether it was necessarily transformed to malic acid prior to oxidation. It was shown with bacteria, using the methylene blue technique [Quastel and The evidence was sufficient to justify the opinion that fumaric acid might be oxidised directly. The discovery, however, that the donating powers of malic acid might be obscured by the accepting powers of the acid-presumably through the formation of fumaric acid which is a ready hydrogen acceptor-vitiated this conclusion, and later on the formulation of the theory of activation The question, therefore, was left quite open. Most tissues and organisms can bring about a change of fumaric acid to l-malic acid and can accomplish the oxidation of the latter acid, but neither of these facts constitutes evidence that the main line of oxidation of fuimaric acid lies through l-malic acid. In the case of certain bacteria, for instance, fumaric acid gives rise (in presence of ammonium ions) to 1-aspartic acid, an amino-acid capable of being oxidised by the bacteria in question. But it cannot be assumed from these facts that the main line of oxidation of fumaric acid, with these bacteria, lies through l-aspartic acid. The actual finding among the products of oxidation of succinate or fumarate