The effect of dihydroxyacetone phosphate and 3-phosphoglycerate on O2 evolution and on the levels of ATP, ADP and Pi in isolated intact chloroplasts.

Addition of dihydroxyacetone phosphate (2.5 mM) or 3-phosphoglycerate (2.5 mM) to a suspension of isolated intact chloroplasts, which contains Pi only in low concentrations (0.2 mM) leads to a competitive inhibition of Pi uptake in the light. In consequence, the ATP/ADP ratio is strongly decreased. The rate of O2 evolution is also reduced under these conditions, but the degree of inhibition is much higher after addition of dihydroxyacetone phosphate than after addition of 3-phosphoglycerate. Therefore, besides the competitive inhibition of Pi uptake, additional effects of dihydroxyacetone phosphate and 3-phosphoglycerate on O2 evolution and CO2 fixation of isolated intact chloroplasts must occur, which are discussed.