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A rapid‐equilibrium model for the control of the Calvin photosynthesis cycle by cytosolic orthophosphate

Pettersson, Gösta LU and Ryde-Pettersson, Ulf LU (1987) In European Journal of Biochemistry 169(2). p.423-429
Abstract

A simple model based on rapid‐equilibrium assumptions is derived which relates the steady‐state activity of the Calvin cycle for photosynthetic carbohydrate formation in C3 plants to the kinetic properties of a single cycle enzyme (fructose bisphosphatase) and of the phosphate translocator which accounts for the export of photosynthate from the chloroplast. Depending on the kinetic interplay of these two catalysts, the model system may exhibit a single or two distinct modes of steady‐state operation, or may be unable to reach a steady state. The predictions of the model are analysed with regard to the effect of external orthophosphate on the steady‐state rate of photosynthesis in isolated chloroplasts under conditions of... (More)

A simple model based on rapid‐equilibrium assumptions is derived which relates the steady‐state activity of the Calvin cycle for photosynthetic carbohydrate formation in C3 plants to the kinetic properties of a single cycle enzyme (fructose bisphosphatase) and of the phosphate translocator which accounts for the export of photosynthate from the chloroplast. Depending on the kinetic interplay of these two catalysts, the model system may exhibit a single or two distinct modes of steady‐state operation, or may be unable to reach a steady state. The predictions of the model are analysed with regard to the effect of external orthophosphate on the steady‐state rate of photosynthesis in isolated chloroplasts under conditions of saturating light and CO2. Due to the possible existence of two distinct steady states, the model may account for the stimulatory as well as the inhibitory effects of external phosphate observed in experiments with intact chloroplasts. Stability arguments indicate, however, that only the steady‐state case corresponding to phosphate inhibition of the rate of photosynthesis could be of physiological interest. It is concluded that chloroplasts under physiological conditions most likely operate in a high‐velocity steady state characterized by a negative Calvin cycle flux control coefficient for the phosphate translocator. This means that any factor enhancing the export capacity of the phosphate translocator can be anticipated to decrease the actual steady‐state rate of photosynthate export due to a decreased steady‐state rate of cyelic photosynthate production. Copyright © 1987, Wiley Blackwell. All rights reserved

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
European Journal of Biochemistry
volume
169
issue
2
pages
7 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:0023474323
ISSN
0014-2956
DOI
10.1111/j.1432-1033.1987.tb13629.x
language
English
LU publication?
yes
id
1a4cd85d-7b84-4b87-ab06-a41946be7a5f
date added to LUP
2017-02-04 11:25:31
date last changed
2017-05-01 20:38:05
@article{1a4cd85d-7b84-4b87-ab06-a41946be7a5f,
  abstract     = {<p>A simple model based on rapid‐equilibrium assumptions is derived which relates the steady‐state activity of the Calvin cycle for photosynthetic carbohydrate formation in C<sub>3</sub> plants to the kinetic properties of a single cycle enzyme (fructose bisphosphatase) and of the phosphate translocator which accounts for the export of photosynthate from the chloroplast. Depending on the kinetic interplay of these two catalysts, the model system may exhibit a single or two distinct modes of steady‐state operation, or may be unable to reach a steady state. The predictions of the model are analysed with regard to the effect of external orthophosphate on the steady‐state rate of photosynthesis in isolated chloroplasts under conditions of saturating light and CO<sub>2</sub>. Due to the possible existence of two distinct steady states, the model may account for the stimulatory as well as the inhibitory effects of external phosphate observed in experiments with intact chloroplasts. Stability arguments indicate, however, that only the steady‐state case corresponding to phosphate inhibition of the rate of photosynthesis could be of physiological interest. It is concluded that chloroplasts under physiological conditions most likely operate in a high‐velocity steady state characterized by a negative Calvin cycle flux control coefficient for the phosphate translocator. This means that any factor enhancing the export capacity of the phosphate translocator can be anticipated to decrease the actual steady‐state rate of photosynthate export due to a decreased steady‐state rate of cyelic photosynthate production. Copyright © 1987, Wiley Blackwell. All rights reserved</p>},
  author       = {Pettersson, Gösta and Ryde-Pettersson, Ulf},
  issn         = {0014-2956},
  language     = {eng},
  number       = {2},
  pages        = {423--429},
  publisher    = {Wiley-Blackwell},
  series       = {European Journal of Biochemistry},
  title        = {A rapid‐equilibrium model for the control of the Calvin photosynthesis cycle by cytosolic orthophosphate},
  url          = {http://dx.doi.org/10.1111/j.1432-1033.1987.tb13629.x},
  volume       = {169},
  year         = {1987},
}