The Oxidation of d-isoCitrate by Pea-seedling Mitochondria

A diphosphopyridine nucleotide specific isocitric dehydrogenasehas been isolated from pea-seedling mitochondria and purified10-fold. In the presence of manganese the enzyme catalyses theoxidative decarboxylation of d-isocitrate to -oxoglutarate andCO₂, but under similar conditions does not catalyse the reversereaction. Evidence is presented indicating that -SH groups ofthe enzyme are essential for activity. The properties of theenzyme are described.