Regular Paper

Photosynthesis Research

, Volume 23, Issue 3, pp 257-268

First online:

Glyoxylate inhibition of ribulosebisphosphate carboxylase/oxygenase activation in intact, lysed, and reconstituted chloroplasts

  • William J. CampbellAffiliated withDepartment of Agronomy, University of Illinois
  • , William L. OgrenAffiliated withDepartment of Agronomy, University of IllinoisAgricultural Research Service, United States Department of Agriculture

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


At bicarbonate concentrations equivalent to air levels of CO2, activation of ribulosebisphosphate carboxylase/oxygenase (rubisco) was inhibited by micromolar concentrations of glyoxylate in intact, lysed, and reconstituted chloroplasts and in stromal extracts. The concentration of glyoxylate required for 50% inhibition of light activation in intact chloroplasts was estimated to be 35 micromolar. No direct inhibition by glyoxylate was observed with purified rubisco or rubisco activase at micromolar concentrations. Levels of ribulose 1,5-bisphosphate and ATP increased in intact chloroplasts following glyoxylate treatment. Results from experiments with well-buffered lysed and reconstituted chloroplast systems ruled out lowering of pH as the cause of inhibition. With intact chloroplasts, micromolar glyoxylate did not prevent activation of rubisco at high (10 mM) concentrations of bicarbonate, indicating that rubisco could be spontaneously activated in the presence of glyoxylate. These results suggest the existence of a component of the in vivo rubisco activation system that is not yet identified and which is inhibited by glyoxylate.

Key words

photosynthesis rubisco activase rubisco activation