Die Stöchiometrie der Photosynthese in isolierten Chloroplasten
2014
Jacobi, Günter
As reported previously there is no stoichiometry between the amounts of ATP and NADPH₂ formed in light by isolated chloroplasts of spinach. The amount of esterified inorganic phosphate is always too low. However, addition of ascorbate leads to an increase of ATP- but not of NADPH₂-formation, independent of the gas phase present. Further experiments indicated that for the formation of “extra”-ATP with limiting amounts of NADP in long term experiments aerobic conditions are required. This additional ATP-formation occurs only in presence of ascorbate and starts when all NADP has been photoreduced. Ascorbate alone leads to photophosphorylation different from those systems, in which ascorbate is used as electron donor. The ascorbate induced photophosphorylation is strongly inhibited by o-phenanthroline and partly by cyanide. It is assumed that this ATP-formation is coupled with an oxygen exchange via a redox compound such as indophenol at the level of the second light reaction.
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