Photosynthesis in a reconstituted chloroplast system from spinach. Some factors affecting CO2-dependent oxygen evolution with fructose-1,6-bisphosphate as substrate.
When envelope-free spinach chloroplasts are incubated with stromal protein, catalytic NADP, catalytic ADP, radioactive bicarbonate and fructose 1,6-bisphosphate, 14CO2 fixation starts immediately upon illumination but oxygen evolution is delayed. The delay is increased by the addition of fructose 6-phosphate and by a variety of factors known (or believed) to increase fructose bisphosphatase activity (such as dithiothreitol, more alkaline pH, higher [Mg] and antimycin A). Conversely, the lag can be decreased or eliminated by the addition of an ATP-generating system. Bearing in mind the known inhibition, by ADP, of sn-phospho-3-glycerate (3-phosphoglycerate) reduction it is concluded that the lag in O2 evolution results from the production of ribulose 5-phosphate from fructose bisphosphate and that this in turn inhibits the reoxidation of NADPH by adversely affecting the ADP/ATP ratio. The results are discussed in their relation to the mode of action of antimycin A and to regulation of the reductive pentose phosphate pathway.
D002245:Carbon Dioxide / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D028744:Ethics Committees, Research / Q000592:standards; D006597:Fructose-Bisphosphatase / Q000378:metabolism; D005636:Fructosephosphates / Q000378:metabolism*; D006598:Hexosediphosphates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010788:Photosynthesis / Q000187:drug effects; D010944:Plants
D005636:Fructosephosphates; D006598:Hexosediphosphates; D002245:Carbon Dioxide; D006597:Fructose-Bisphosphatase; D008274:Magnesium; D010100:Oxygen; D004229:Dithiothreitol