High activities of NADP+-dependent isocitrate dehydrogenase and malic enzyme in rabbit lens epithelial cells.

Measurements were made of the activities of the NADP+-dependent isocitrate dehydrogenase, malic enzyme and glucose-6-phosphate dehydrogenase in cytosolic supernatants of whole lens and capsule-epithelium. The activities of all three NADP+-dependent enzymes were concentrated in the capsule-epithelium relative to the activities measured in the whole lens. These results show for the first time that the rabbit lens epithelial cells contain substantial activities of the NADP+-dependent isocitrate dehydrogenase and malic enzyme. It is proposed that these enzymes together with glucose-6-phosphate dehydrogenase are involved in the regulation of the intracellular level of glutathione during oxidative stress by providing the NADPH necessary for the activity of glutathione reductase.