Abstract
The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined. An 11-fold variation in HK activity resulted in altered root growth, with antisense roots growing better than sense roots. Quantification of sugars, organic acids and amino acids in transgenic roots demonstrated that the manipulation of HK activity had very little effect on the intracellular pools of these metabolites. However, adenylate and free Pi levels were negatively affected by an increase in HK activity. The flux control coefficient of HK over the phosphorylation of glucose was measured for the first time in plants. Its value varied with HK level. It reached 1.71 at or below normal HK activity value and was much lower (0.32) at very high HK levels. Measurements of glycolytic flux and O(2) uptake rates demonstrated that the differences in glucose phosphorylation did not affect significantly glycolytic and respiratory metabolism. We hypothesized that these results could be explained by the existence of a futile cycle between the pools of hexose-Ps and carbohydrates. This view is supported by several lines of evidence. Firstly, activities of enzymes capable of catalyzing these reactions were detected in roots, including a hexose-P phosphatase. Secondly, metabolic tracer experiments using (14)C-glucose as precursor showed the formation of (14)C-fructose and (14)C-sucrose. We conclude that futile cycling of hexose-P could be partially responsible for the differences in energetic status in roots with high and low HK activity and possibly cause the observed alterations in growth in transgenic roots. The involvement of HK and futile cycles in the control of glucose-6P metabolism is discussed.
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Claims 10
Claim · model-written summary
Antisense potato roots with lower hexokinase activity grew better than sense roots.
- Taxon
- potato
Solanum tuberosume0 - Treatment
- over- and underexpressing hexokinasee0
- Gene
- hexokinasee0
- Outcome
- root growthe1
- Direction
- growing bettere1
- Comparator
- sense rootse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e1“An 11-fold variation in HK activity resulted in altered root growth, with antisense roots growing better than sense roots”
Claim · model-written summary
Manipulating hexokinase activity had very little effect on intracellular sugar, organic acid and amino acid pools in potato roots.
- Taxon
- potatoSolanum tuberosume0
- Treatment
- manipulation of HK activitye2
- Outcome
- intracellular pools of these metabolitese2
- Direction
- no_changeinferrede2
- Qualifier
- very little effecte2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e2“Quantification of sugars, organic acids and amino acids in transgenic roots demonstrated that the manipulation of HK activity had very little effect on the intracellular pools of these metabolites”
Claim · model-written summary
An increase in hexokinase activity negatively affected adenylate and free Pi levels in potato roots.
- Taxon
- potatoSolanum tuberosume0
- Treatment
- an increase in HK activitye3
- Outcome
- adenylate and free Pi levelse3
- Direction
- negatively affectede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e3“However, adenylate and free Pi levels were negatively affected by an increase in HK activity”
Claim · model-written summary
The flux control coefficient of HK over glucose phosphorylation reached 1.71 at or below normal HK activity.
- Taxon
- potatoSolanum tuberosume0
- Outcome
- flux control coefficient of HK over the phosphorylation of glucosee4
- Value
- 1.71e5
- Qualifier
- at or below normal HK activity valuee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e4“The flux control coefficient of HK over the phosphorylation of glucose was measured for the first time in plants”
e5“It reached 1.71 at or below normal HK activity value and was much lower (0.32) at very high HK levels”
Claim · model-written summary
The flux control coefficient of HK over glucose phosphorylation was much lower (0.32) at very high HK levels.
- Taxon
- potatoSolanum tuberosume0
- Outcome
- flux control coefficient of HK over the phosphorylation of glucosee4
- Direction
- much lowere5
- Value
- 0.32e5
- Qualifier
- at very high HK levelse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e4“The flux control coefficient of HK over the phosphorylation of glucose was measured for the first time in plants”
e5“It reached 1.71 at or below normal HK activity value and was much lower (0.32) at very high HK levels”
Claim · model-written summary
Differences in glucose phosphorylation did not significantly affect glycolytic and respiratory metabolism in potato roots.
- Taxon
- potatoSolanum tuberosume0
- Treatment
- differences in glucose phosphorylatione6
- Outcome
- glycolytic and respiratory metabolisme6
- Direction
- no_changeinferrede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e6“Measurements of glycolytic flux and O(2) uptake rates demonstrated that the differences in glucose phosphorylation did not affect significantly glycolytic and respiratory metabolism”
Claim · model-written summary
The results may be explained by a futile cycle between the pools of hexose-Ps and carbohydrates.
- Taxon
- potatoSolanum tuberosume0
- Outcome
- these resultse7
- Qualifier
- a futile cycle between the pools of hexose-Ps and carbohydratese7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e7“We hypothesized that these results could be explained by the existence of a futile cycle between the pools of hexose-Ps and carbohydrates”
Claim · model-written summary
Enzymes capable of catalysing the futile cycle reactions, including a hexose-P phosphatase, were detected in potato roots.
- Taxon
- potatoSolanum tuberosume0
- Organ / stage
- rootse1
- Gene
- hexose-P phosphatasee1
- Outcome
- activities of enzymes capable of catalyzing these reactionse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e1“Firstly, activities of enzymes capable of catalyzing these reactions were detected in roots, including a hexose-P phosphatase”
Claim · model-written summary
Tracer experiments with (14)C-glucose showed formation of (14)C-fructose and (14)C-sucrose in potato roots.
- Taxon
- potatoSolanum tuberosume0
- Treatment
- (14)C-glucosee1
- Outcome
- formation of (14)C-fructose and (14)C-sucrosee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e1“Secondly, metabolic tracer experiments using (14)C-glucose as precursor showed the formation of (14)C-fructose and (14)C-sucrose”
Claim · model-written summary
Futile cycling of hexose-P could be partially responsible for the differences in energetic status in roots with high and low HK activity.
- Taxon
- potatoSolanum tuberosume0
- Outcome
- differences in energetic status in rootse1
- Qualifier
- futile cycling of hexose-P could be partially responsiblee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined”
e1“We conclude that futile cycling of hexose-P could be partially responsible for the differences in energetic status in roots with high and low HK activity and possibly cause the observed alterations in growth in transgenic roots”
The same questions in other papers
glucose · molecular: metabolites · Solanum tuberosum (potato)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.