Model studies of the regulation of the Calvin photosynthesis cycle by cytosolic metabolites.
A kinetic model for photosynthetic carbohydrate formation in the chloroplast of C3 plants is presented which includes consideration of the interaction of the phosphate translocator of the chloroplast envelope with external reactants such as 3-phosphoglycerate, dihydroxyacetone phosphate, and glyceraldehyde 3-phosphate in addition to inorganic (ortho)phosphate. The model is shown to account satisfactorily for experimentally observed effects of such reactants on the rates of carbon dioxide fixation and starch production in isolated chloroplast. The predictions of the model with regard to the regulation of stromal processes of photosynthetic carbohydrate formation by cytosolic concentration variables have been examined. The results indicate that the cytosolic concentrations of metabolites that interact with the phosphate translocator represent important regulatory signals. Increasing levels of exported photosynthate (phosphoglycerates and triose phosphates) in the cytosol do not suppress the rate of photosynthetic carbon dioxide fixation, but redirects reaction flux such that starch production within the chloroplasts is favoured at the expense of a decreased rate of photosynthate export to the cytosol.
Pettersson
G
G
Department of Biochemistry, University of Lund, Sweden.
Ryde-Pettersson
U
U
D002245:Carbon Dioxide / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000502:physiology*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004099:Dihydroxyacetone Phosphate / Q000494:pharmacology; D005988:Glyceric Acids / Q000494:pharmacology; D007700:Kinetics; D008954:Models, Biological; D028044:Phosphate-Binding Proteins; D010710:Phosphates / Q000378:metabolism; D010788:Photosynthesis; D018521:Plant Physiological Phenomena
D002352:Carrier Proteins; D005988:Glyceric Acids; D028044:Phosphate-Binding Proteins; D010710:Phosphates; D002245:Carbon Dioxide; D004099:Dihydroxyacetone Phosphate; C005156:3-phosphoglycerate