LOCALIZATION OF PYRUVATE-DEHYDROGENASE COMPLEX IN PISUM-SATIVUM CHLOROPLASTS

Purified Pisum sativum chloroplasts showed the presence of all three components of the pyruvate-dehydrogenase complex (PDC). Radiotracer studies indicated activity of the pyruvate-decarboxylase component and the lipoate-transacetylase component. The dehydrogenase activity was detected spectrophotometrically. On zone-type sucrose density gradients, PDC peaked coincidentally with the intact-chloroplast band, which is free from mitochondrial contamination. Further studies with mitochondria and chloroplasts purified by repeated sedimentation and resuspension showed reduced activities of both mitochondrial and chloroplastic PDC in the absence of cofactors. Acetyl coenzyme A generated internally via pyruvate may serve as the main source of carbon for chloroplastic fatty-acid synthesis. © 1979.