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- Title
Quantitative Evaluation of the Rate of 3-Phosphoglycerate Reduction in Chloroplasts.
- Authors
Fridlyand, Leonid E.; Backhausen, Jan E.; Holtgrefe, Simone; Kitzmann, Camillo; Scheibe, Renate
- Abstract
The 3-phosphoglycerate reduction has often been considered as a rate-limiting step in photosynthesis. To investigate this, a kinetic equation for 3-phosphoglycerate reduction is developed. The reaction catalyzed by 3-phosphoglycerate kinase was considered as close to the thermo-dynamic equilibrium and that of NADP-linked glyceral-dehyde 3-phosphate dehydrogenase as Michaelis-Menten type. Isolated intact spinach chloroplasts were used to obtain the data that are required to apply the equation for a description of photosynthesis in vivo. The apparent Km for 1,3-bisphosphoglycerate is evaluated to be 0.95 μM in isolated chloroplasts. The temperature dependence of the activity of NADP-linked glyceraldehyde 3-phosphate dehydrogenase is determined; the Q10 is 1.8 between 15° and 25°C. Numerous examples are presented where the developed kinetic equation is used to describe the reaction rate in the isolated chloroplast as well as in the leaf under steady-state and induction conditions. It is shown that within the physiological range, the rate of 3-phosphoglycerate reduction can be estimated by measuring the activity of NADP-linked glyceraldehyde 3-phosphate dehydrogenase,. the [ATP]/[ADP] ratio and the 3-phosphoglycerate concentration. It is shown that the assumption of a thermodynamic equilibrium at the 3-phosphoglycerate reduction cannot be reconciled with existing experimental data. The possible limiting role of NADP-linked glyceraldehyde 3-phosphate dehydrogenase in the Calvin cycle is discussed.
- Subjects
CHLOROPLASTS; PHOTOSYNTHESIS; PHOSPHOGLYCERATE kinase; NICOTINAMIDE adenine dinucleotide phosphate; MICHAELIS-Menten equation; QUANTITATIVE research; ADENOSINE triphosphate
- Publication
Plant & Cell Physiology, 1997, Vol 38, Issue 11, p1177
- ISSN
0032-0781
- Publication type
Article
- DOI
10.1093/oxfordjournals.pcp.a029104