THE ENZYMATIC MECHANISM OF OXIDATION-REDUCTIONS BETWEEN MALATE OR ISOCITRATE AND PYRUVATE

Abstract

The discovery of carbon dioxide assimilation by heterotrophic bacteria (1) and animal tissues (2) aroused considerable interest in the mechanisms involved.Evidence from various sources suggested the Wood and Werkman reaction, i.e. the carboxylation of pyruvate to oxalacetate, as a major pathway (3).Evans, Vennesland, and Slotin (4) discovered that pigeon liver extracts fixed ('02 in the presence of malate (or fumarate), pyruvate, and catalytic amounts of manganous ions and of either diphosphopyridine nucleotide (DPN) or triphosphopyridine nucleotide (TPN), while catalyzing the overall Reaction 1.(1) Malate (or fumarate + HtO) + pyruvate -+ pyruvate + CO* + lactate This is essentially a dismutation between malate, which is oxidized and decarboxylated to pyruvate + ('02, and pyruvate, which is reduced to lactate; it will be referred to as the malate-pyruvate dismutation.Further work (4, 5) suggested that Reaction 1 is the net result of the following reactions.(2) Fumarate + HnO ti malate (3) Malate + pyridine nucleotide & oxalacetate + dihydropyridine