| 1. |
- Pettersson, Gösta, et al.
(författare)
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Model studies of the regulation of the Calvin photosynthesis cycle by cytosolic metabolites
- 1990
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Ingår i: Biomedica Biochimica Acta. - 0232-766X. ; 49:8-9, s. 723-732
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Tidskriftsartikel (refereegranskat)abstract
- 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 photosynthetic (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 chloroplast is favoured at the expense of a decreased rate of photosynthate export to the cytosol.
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| 2. |
- Ryde-Pettersson, Ulf
(författare)
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Identification of possible two‐reactant sources of oscillations in the Calvin photosynthesis cycle and ancillary pathways
- 1991
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 198:3, s. 613-619
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Tidskriftsartikel (refereegranskat)abstract
- A systematic search for possible sources of experimentally observed oscillations in the photosynthetic reaction system has been performed by application of recent theoretical results characterizing the transient‐state rate behaviour of metabolic reactions involving two independent concentration variables. All subsystems involving two independent reactants in metabolically fundamental parts of the Calvin cycle and the ancillary pathways of starch and sucrose synthesis have been examined in order to decide on basis of their kinetic and stoichiometric structure whether or not they may trigger oscillations. The results show that no less than 20 possible oscillators can be identified in the examined reaction system, only three of which have been previously considered as potential sources of experimentally observed oscillations. This illustrates the superiority of the method now applied over those previously used to identify possible two‐reactant sources of metabolic oscillations and indicates that there should be no difficulty in complex metabolic pathways to point to a multitude of interactions that may trigger an oscillatory rate behaviour of the system.
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| 3. |
- Ryde-Pettersson, Ulf
(författare)
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On the mechanistic origin of damped oscillations in biochemical reaction systems
- 1990
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 194:2, s. 431-436
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Tidskriftsartikel (refereegranskat)abstract
- A generalized reaction scheme for the kinetic interaction of two reactants in a metabolic pathway has been examined in order to establish what minimal mechanistic patterns are required to support a damped oscillatory transient‐state kinetic behaviour of such a two‐component system when operating near a steady state. All potentially oscillating sub‐systems inherent in this scheme are listed and briefly characterized. The list includes several mechanistic patterns that may be frequently encountered in biological system (e.g. involving feedback inhibition, feed‐forward activation, substrate inhibition or product activation), but also draw attention to some hitherto unforeseen mechanisms by which the kinetic interaction of two metabolites may trigger damped oscillations. The results can be used to identify possible sources of oscillations in metabolic pathways without detailed knowledge about the explicit rate equations that apply.
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| 4. |
- Ryde-Pettersson, Ulf
(författare)
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Oscillations in coupled enzymic reactions at high concentration of enzyme
- 1992
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Ingår i: BBA - Protein Structure and Molecular Enzymology. - 0167-4838. ; 1119:2, s. 118-122
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Tidskriftsartikel (refereegranskat)abstract
- The transient-state kinetic consequences of the coupling of a single-enzyme reaction to other metabolic reactions have been examined in generalized terms. Analytical data are presented which specify under what conditions such coupling may lead to an oscillatory transient rate behaviour of a reaction system involving an enzyme operating by a Michaelian mechanism. The results indicate that the presence of enzyme in concentrations comparable to those of substrate and product may represent a hitherto unforeseen possible source of weakly damped, or even sustained, oscillations in metabolic networks. This observation has some important implications with regard to the occurrence of oscillations in biochemical reaction systems and to transient-state kinetic modelling of metabolic systems.
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