Inhibition of photosynthetic carbon metabolism in isolated chloroplasts by iodoacetol phosphate

Carbon dioxide-dependent and 3-phosphoglycerate (PGA)-dependent O₂ evolution by isolated chloroplasts of wheat is inhibited by micromolar levels of iodoacetol phosphate (IAP). Loss of the activity is time-dependent and a higher concentration of PGA increases the half-time for inhibition (e.g. at 40 micromolar IAP the half-time is about 0.5 minutes at 1 millimolar PGA compared to 1.5 minutes at 10 millimolar PGA). A marked inhibition of NADP glyceraldehyde-3-P dehydrogenase was observed when chloroplasts were pretreated with micromolar levels of IAP, osmotically shocked, and several stromal enzymes assayed.