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Mechanism of Metabolite transfer between Enzymes in Glycolysis and Connected Pathways

Martinez Arias, Wilma LU (1997)
Abstract
The metabolite produced by one enzyme in a metabolic pathway can be transferred to the next enzyme in the pathway by free diffusion via solution or by channelling in an enzyme-enzyme complex without prior release of the metabolite to solution. While metabolite channelling is known to occur in systems where stable multienzyme complexes form, conflicting views have been expressed as to its existence in pathways involving "soluble" enzymes. This thesis examines the kinetic evidence that has been presented in support of a direct (channelled) metabolite transfer between soluble enzymes in glycolysis and connected pathways.



More specifically, transient-state kinetic studies have been performed to test the proposal that there... (More)
The metabolite produced by one enzyme in a metabolic pathway can be transferred to the next enzyme in the pathway by free diffusion via solution or by channelling in an enzyme-enzyme complex without prior release of the metabolite to solution. While metabolite channelling is known to occur in systems where stable multienzyme complexes form, conflicting views have been expressed as to its existence in pathways involving "soluble" enzymes. This thesis examines the kinetic evidence that has been presented in support of a direct (channelled) metabolite transfer between soluble enzymes in glycolysis and connected pathways.



More specifically, transient-state kinetic studies have been performed to test the proposal that there is a channelled transfer of glyceraldehyde-3-phosphate from aldolase to glyceraldehyde-3-phosphate dehydrogenase. We found that this proposal is based on a misinterpretation of kinetic data that are actually fully consistent with a free-diffusion mechanism of metabolite transfer. Furthermore, the much-discussed hypothesis that a channelled transfer of NADH occurs between dehydrogenases of distinct coenzyme specificity has been tested by crucial steady-state and transient-state kinetic experiments. Our results lend no support to this hypothesis, but are fully consistent with a free-diffusion mechanism of NADH transfer.



It is concluded that no tenable kinetic evidence presently is available for a channelled transfer of metabolites between enzymes that do not form stable multienzyme complexes. (Less)
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author
opponent
  • Prof. Mannervik, Bengt, Uppsala University
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Channelling, Free-diffusion, Glycolytic pathway, Dehydrogenases, Enzyme kinetics, Biochemistry, Metabolite transfer mechanism., Biokemi, Metabolism
pages
74 pages
defense location
N/A
defense date
1997-12-15 10:15
external identifiers
  • Other:ISRN: LUNKDL-(NKBK-1056)-1-74/97
ISBN
91-628-2812-6
language
English
LU publication?
yes
id
889fa586-2d9a-48af-9923-bcceee4a3636 (old id 29727)
date added to LUP
2007-06-13 11:31:52
date last changed
2016-09-19 08:45:18
@misc{889fa586-2d9a-48af-9923-bcceee4a3636,
  abstract     = {The metabolite produced by one enzyme in a metabolic pathway can be transferred to the next enzyme in the pathway by free diffusion via solution or by channelling in an enzyme-enzyme complex without prior release of the metabolite to solution. While metabolite channelling is known to occur in systems where stable multienzyme complexes form, conflicting views have been expressed as to its existence in pathways involving "soluble" enzymes. This thesis examines the kinetic evidence that has been presented in support of a direct (channelled) metabolite transfer between soluble enzymes in glycolysis and connected pathways.<br/><br>
<br/><br>
More specifically, transient-state kinetic studies have been performed to test the proposal that there is a channelled transfer of glyceraldehyde-3-phosphate from aldolase to glyceraldehyde-3-phosphate dehydrogenase. We found that this proposal is based on a misinterpretation of kinetic data that are actually fully consistent with a free-diffusion mechanism of metabolite transfer. Furthermore, the much-discussed hypothesis that a channelled transfer of NADH occurs between dehydrogenases of distinct coenzyme specificity has been tested by crucial steady-state and transient-state kinetic experiments. Our results lend no support to this hypothesis, but are fully consistent with a free-diffusion mechanism of NADH transfer.<br/><br>
<br/><br>
It is concluded that no tenable kinetic evidence presently is available for a channelled transfer of metabolites between enzymes that do not form stable multienzyme complexes.},
  author       = {Martinez Arias, Wilma},
  isbn         = {91-628-2812-6},
  keyword      = {Channelling,Free-diffusion,Glycolytic pathway,Dehydrogenases,Enzyme kinetics,Biochemistry,Metabolite transfer mechanism.,Biokemi,Metabolism},
  language     = {eng},
  pages        = {74},
  title        = {Mechanism of Metabolite transfer between Enzymes in Glycolysis and Connected Pathways},
  year         = {1997},
}