Journal Article

Quantitative Evaluation of the Rate of 3-Phosphoglycerate Reduction in Chloroplasts

Leonid E. Fridlyand, Jan E. Backhausen, Simone Holtgrefe, Camillo Kitzmann and Renate Scheibe

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 38, issue 11, pages 1177-1186
Published in print January 1997 | ISSN: 0032-0781
Published online January 1997 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/oxfordjournals.pcp.a029104
Quantitative Evaluation of the Rate of 3-Phosphoglycerate Reduction in Chloroplasts

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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.

Keywords: ATP/ADP ratio; Chloroplast; CO2 assimilation; Kinetic equation; NADP-linked glyceraldehyde 3-phosphate dehydrogenase

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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