Abstract
The effects of adenine nucleotides on pea seed glutamine synthetase (EC 6.3.1.2) activity were examined as a part of our investigation of the regulation of this octameric plant enzyme. Saturation curves for glutamine synthetase activity versus ATP with ADP as the changing fixed inhibitor were not hyperbolic; greater apparent Vmax values were observed in the presence of added ADP than the Vmax observed in the absence of ADP. Hill plots of data with ADP present curved upward and crossed the plot with no added ADP. The stoichiometry of adenine nucleotide binding to glutamine synthetase was examined. Two molecules of [gamma-32P]ATP were bound per subunit in the presence of methionine sulfoximine. These ATP molecules were bound at an allosteric site and at the active site. One molecule of either [gamma-32P]ATP or [14C]ADP bound per subunit in the absence of methionine sulfoximine; this nucleotide was bound at an allosteric site. ADP and ATP compete for binding at the allosteric site, although ADP was preferred. ADP binding to the allosteric site proceeded in two kinetic phases. A Vmax value of 1.55 units/mg was measured for glutamine synthetase with one ADP tightly bound per enzyme subunit; a Vmax value of 0.8 unit/mg was measured for enzyme with no adenine nucleotide bound at the allosteric site. The enzyme activation caused by the binding of ADP to the allosteric sites was preceded by a lag phase, the length of which was dependent on the ADP concentration. Enzyme incubated in 10 mM ADP bound approximately 4 mol of ADP/mol of native enzyme before activation was observed; the activation was complete when 7-8 mol of ADP were bound per mol of the octameric, native enzyme. The Km for ATP (2 mM) was not changed by ADP binding to the allosteric sites. ADP was a simple competitive inhibitor (Ki = 0.05 mM) of ATP for glutamine synthetase with eight molecules of ADP tightly bound to the allosteric sites of the octamer. Binding of ATP to the allosteric sites led to marked inhibition.
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Claims 16
Claim · model-written summary
Glutamine synthetase saturation curves against ATP with ADP as inhibitor were not hyperbolic.
- Taxon
- pea
Lathyrus oleraceust0 - Gene
- glutamine synthetasee0
- Compound
- ADPe0
- Outcome
- not hyperbolice0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Saturation curves for glutamine synthetase activity versus ATP with ADP as the changing fixed inhibitor were not hyperbolic”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Added ADP increased apparent Vmax compared with its absence.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- added ADPe0
- Gene
- glutamine synthetaset0
- Outcome
- apparent Vmaxe0
- Direction
- greatere0
- Comparator
- absence of ADPe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“greater apparent Vmax values were observed in the presence of added ADP than the Vmax observed in the absence of ADP”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Hill plots with ADP curved upward and crossed the plot without added ADP.
- Taxon
- peaLathyrus oleraceust0
- Compound
- ADPe0
- Outcome
- curved upward and crossed the plot with no added ADPe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hill plots of data with ADP present curved upward and crossed the plot with no added ADP.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Two ATP molecules bound per subunit with methionine sulfoximine, at an allosteric and an active site.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- methionine sulfoximinee0
- Outcome
- bound per subunite0
- Value
- Two moleculese0
- Qualifier
- at an allosteric site and at the active sitee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Two molecules of [gamma-32P]ATP were bound per subunit in the presence of methionine sulfoximine. These ATP molecules were bound at an allosteric site and at the active site.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Without methionine sulfoximine, one ATP molecule bound per subunit at an allosteric site.
- Taxon
- peaLathyrus oleraceust0
- Compound
- [gamma-32P]ATPe0
- Outcome
- bound per subunite0
- Value
- One moleculee0
- Qualifier
- in the absence of methionine sulfoximinee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“One molecule of either [gamma-32P]ATP or [14C]ADP bound per subunit in the absence of methionine sulfoximine; this nucleotide was bound at an allosteric site.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Without methionine sulfoximine, one ADP molecule bound per subunit at an allosteric site.
- Taxon
- peaLathyrus oleraceust0
- Compound
- [14C]ADPe0
- Outcome
- bound per subunite0
- Value
- One moleculee0
- Qualifier
- in the absence of methionine sulfoximinee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“One molecule of either [gamma-32P]ATP or [14C]ADP bound per subunit in the absence of methionine sulfoximine; this nucleotide was bound at an allosteric site.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
ADP and ATP competed for allosteric binding, with ADP preferred.
- Taxon
- peaLathyrus oleraceust0
- Compound
- ADPe0
- Outcome
- compete for binding at the allosteric sitee0
- Qualifier
- ADP was preferrede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ADP and ATP compete for binding at the allosteric site, although ADP was preferred.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Allosteric ADP binding proceeded in two kinetic phases.
- Taxon
- peaLathyrus oleraceust0
- Outcome
- ADP bindinge0
- Value
- two kinetic phasese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ADP binding to the allosteric site proceeded in two kinetic phases.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Vmax was 1.55 units/mg with one ADP tightly bound per subunit.
- Taxon
- peaLathyrus oleraceust0
- Outcome
- Vmaxe0
- Value
- 1.55 units/mge0
- Qualifier
- one ADP tightly bound per enzyme subunite0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A Vmax value of 1.55 units/mg was measured for glutamine synthetase with one ADP tightly bound per enzyme subunit”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Vmax was 0.8 unit/mg without allosterically bound adenine nucleotide.
- Taxon
- peaLathyrus oleraceust0
- Outcome
- Vmaxe0
- Value
- 0.8 unit/mge0
- Qualifier
- no adenine nucleotide bound at the allosteric sitee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a Vmax value of 0.8 unit/mg was measured for enzyme with no adenine nucleotide bound at the allosteric site.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
ADP-induced enzyme activation followed a lag whose length depended on ADP concentration.
- Taxon
- peaLathyrus oleraceust0
- Compound
- ADPe0
- Outcome
- lag phasee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The enzyme activation caused by the binding of ADP to the allosteric sites was preceded by a lag phase, the length of which was dependent on the ADP concentration.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
In 10 mM ADP, about four ADP molecules per native enzyme bound before activation.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- 10 mM ADPe0
- Outcome
- bounde0
- Value
- approximately 4 mol of ADP/mol of native enzymee0
- Qualifier
- before activation was observede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Enzyme incubated in 10 mM ADP bound approximately 4 mol of ADP/mol of native enzyme before activation was observed”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Activation was complete with seven to eight ADP molecules bound per octameric enzyme.
- Taxon
- peaLathyrus oleraceust0
- Outcome
- activation was completee0
- Value
- 7-8 mol of ADPe0
- Qualifier
- per mol of the octameric, native enzymee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the activation was complete when 7-8 mol of ADP were bound per mol of the octameric, native enzyme.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Allosteric ADP binding did not change the ATP Km of 2 mM.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- ADP binding to the allosteric sitese0
- Outcome
- Km for ATPe0
- Direction
- not changede0
- Value
- 2 mMe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Km for ATP (2 mM) was not changed by ADP binding to the allosteric sites.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
ADP competitively inhibited ATP with Ki 0.05 mM when eight ADP molecules were tightly bound to the octamer's allosteric sites.
- Taxon
- peaLathyrus oleraceust0
- Compound
- ADPe0
- Outcome
- simple competitive inhibitore0
- Value
- 0.05 mMe0
- Qualifier
- eight molecules of ADP tightly bound to the allosteric sites of the octamere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ADP was a simple competitive inhibitor (Ki = 0.05 mM) of ATP for glutamine synthetase with eight molecules of ADP tightly bound to the allosteric sites of the octamer.”
t0“pea seed glutamine synthetase”
Claim · model-written summary
Allosteric ATP binding markedly inhibited the enzyme.
- Taxon
- peaLathyrus oleraceust0
- Compound
- ATPe0
- Outcome
- marked inhibitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Binding of ATP to the allosteric sites led to marked inhibition.”
t0“pea seed glutamine synthetase”
The same questions in other papers
climate site · molecular: metabolites · Lathyrus oleraceus (pea)Results agree
1 paper in the same direction as this paper
- 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.