Photosynthesis by isolated chloroplasts V. Phosphorylation and carbon dioxide fixation by broken chloroplasts

1. Photosynthetic esterification of inorganic phosphate into adenosine triphosphate, and reduction of CO2 to the level of carbohydrate, hitherto found to occur only in whole chloroplasts, have now been observed with chloroplasts broken by treatment with water. 2. Broken chloroplasts retained only two of the three groups of enzymes contained in whole chloroplasts, namely, those controlling the photolysis of water and photosynthetic phosphorylation. At least some of the enzymes concerned in reduction of CO2 were leached out by treating the chloroplasts with water, with the result that CO2 fixation was completely abolished. 3. On addition of the requisite cofactors, the capacity of broken chloroplasts for photosynthetic phosphorylation was the same as that of whole chloroplasts. 4. The restoration to broken chloroplasts of the full capacity for photosynthetic CO2 fixation of whole chloroplasts required the addition of pyridine nucleotides, adenosine triphosphate, and the soluble enzymes removed by water treatment of whole chloroplasts. 5. An additional several-fold increase in the rate of CO2 fixation by the reconstituted broken chloroplast system was obtained by the further addition of one of several compounds, principally phosphorylated sugars. This has resulted in a level of CO2 fixation by broken chloroplasts which is much higher than that obtained with whole chloroplasts.