Purification and characterization of mitochondrial citrate synthase

Mitochondrial citrate synthase was purified from leaves of Pisum sativum L. cv Progress 9. A three step purification was employed using ATP-Sepharose affinity chromatography which resulted in a 600-fold enrichment. Enzyme activity was assayed spectrophotometrically during greening of etiolated leaves under constant white light illumination. An increase (1.4 fold) in citrate synthase activity was observed in response to light. Immunoblot analysis of the same samples indicated a constant steady state level of citrate synthase on a per milligram protein basis. These investigations provide supportive evidence for the ability of this trichloroacetic acid cycle enzyme to be active in photosynthesizing tissue.