Studies on the Intracellular Location of Enzymes of the Photosynthetic Carbon‐Reduction Cycle

Homogenates of dark‐pretreated leaves yield two particulate fractions in density gradient centrifugation: one contains chlorophyll (chloroplasts) while a second fraction contains ribulose‐1,5‐bisphosphate carboxylase, NADP‐dependent glyceraldehyde‐3‐phosphate dehydrogenase and catalase. Addition of a microbody‐rich pellet to chloroplasts isolated from dark‐pretreated plants largely enhances both oxygen evolution and CO₂‐fixation into organic compounds. The pathway of CO₂ reduction may be part of a membrane system which, under suitable conditions, may separate from the chloroplast as a distinct cytoplasmic entity, having physical properties similar to those of microbodies.