Purification of the isocitric enzyme (triphosphopyridine nucleotide-linked isocitric dehydrogenase–oxalosuccinic carboxylase

Abstract

A method for the purification of triphosphopyridine nucleotide-linked isocitric dehydrogenase and oxalosuccinic carboxylase from pig heart is described. Throughout purification the ratio of isocitric-dehydrogenase activity to oxalosuccinic -carboxylase activity remains constant, and inactivation of the one produces a corresponding inactivation of the other. Sedimentation and diffusion measurements, and electrophoretic analysis at pH 5.6, 7.3 and 8.5, show that the enzyme is a single protein. It was obtained 90-95% pure. Further fractionation of the purified enzyme confirms that it is the component representing 90-95% of the total protein which possesses both isocitric-dehydrogenase and oxalosuccinic-carboxylase activity. The molecular weight of the isocitric enzyme is approximately 64,000.