Planta

, Volume 149, Issue 1, pp 48–51

The mechanism of the control of carbon fixation by the pH in the chloroplast stroma

Studies with acid mediated proton transfer across the envelope
  • U. I. Flügge
  • M. Freisl
  • H. W. Heldt
Article

Abstract

The salts of several weak acids have been used to render the envelope permeable to protons. In order to investigate the role of stromal pH changes in the light regulation of CO2 fixation, formate, octanoate, nitrite, and glyoxylate have been tried as tools to reverse the light-dependent alkalization of the stroma. For this purpose, the decrease of the stromal pH in illuminated spinach chloroplasts, as caused by the addition of these substances or by instantaneous lowering of the pH in the medium, has been compared with the corresponding decrease of CO2 fixation and the change of stromal metabolite levels. It appears from out data that formate and octanoate are suited best to obtain a specific inhibition of CO2 fixation by lowering the stromal pH. The measurement of the corresponding metabolite levels indicates that this inhibition is primarily due to an inhibition of fructose- and sedoheptulose bisphosphatase. It is concluded that these two enzymes are important regulatory steps for the light control of CO2 fixation.

Key words

Chloroplast CO2 fixation Fructose 1.6-bisphosphatase Proton transfer Sedoheptulose 1.7-bisphosphatase Spinacia 

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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • U. I. Flügge
    • 1
  • M. Freisl
    • 1
  • H. W. Heldt
    • 1
  1. 1.Institut für Physiologische Chemie, Physikalische Biochemie und ZellbiologieUniversität MünchenMünchen 2Federal Republic of Germany
  2. 2.Lehrstuhl für Biochemie der Pflanze der Universität GöttingenGöttingenFederal Republic of Germany

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