Abstract
A diphosphopyridine nucleotide specific isocitric dehydrogenase has been isolated from pea-seedling mitochondria and purified 10-fold. In the presence of manganese the enzyme catalyses the oxidative decarboxylation of d-isocitrate to α-oxoglutarate and CO2, but under similar conditions does not catalyse the reverse reaction. Evidence is presented indicating that -SH groups of the enzyme are essential for activity. The properties of the enzyme are described.