Abstract
The reaction of spinach RuBisCO activated with CO2 and Mg2+ proceeded in two phases, an initial burst for a few minutes and the subsequent linear phase, in the presence of saturating concentrations of CO2, ribulose 1,5-bisphosphate (RuBP), and Mg2+. The percentage of the activity in the linear phase to that in the initial burst was 55% with RuBisCO prepared with polyethylene glycol, and very close to the value with the enzyme released immediately from isolated chloro-plasts. RuBisCO prepared with ammonium sulfate had a much larger decrease of the activity in the linear phase. The Euglena enzyme had a linear course of reaction with time for up to 20 minutes. The Km for CO2 of spinach RuBisCO activated beforehand was 20 μM in the initial burst, and 28 μM in the linear phase. In the carboxylase reaction initiated with inactive enzyme, the activity was initially negligible, but in 5 minutes increased to the level observed in the linear phase of the activated enzyme. The Km for CO2 in the linear phase of the pre-inactivated enzyme was 70 μM. The concentration of RuBP was the immediate cause of the two-phasic course of the carboxylase reaction of spinach RuBisCO. The curvature of the time course was not observed below 35 μM RuBP. The enzyme required over 88 μM RuBP for the conventional two-phasic course. Further increase of the concentration of RuBP increased the extent of the curvature, but did not start the curvature sooner after the start of the reaction. Even if spinach RuBisCO was in the linear phase, dilution of RuBP or its consumption by the enzymatic reaction to less than 30 μM caused the enzyme to show the resumed biphasic reaction course after addition of a high concentration of RuBP.
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Claims 13
Claim · model-written summary
Spinach RuBisCO activated with CO2 and Mg2+ showed a two-phase carboxylase reaction, an initial burst of a few minutes followed by a linear phase, under saturating CO2, RuBP and Mg2+.
- Taxon
- Spinach
Spinacia oleraceat0 - Outcome
- two phasese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The reaction of spinach RuBisCO activated with CO2 and Mg2+ proceeded in two phases, an initial burst for a few minutes and the subsequent linear phase”
t0“Spinach”
Claim · model-written summary
With spinach RuBisCO prepared with polyethylene glycol, the activity in the linear phase was 55% of that in the initial burst.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- polyethylene glycole0
- Outcome
- percentage of the activity in the linear phase to that in the initial burste0
- Value
- 55%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The percentage of the activity in the linear phase to that in the initial burst was 55% with RuBisCO prepared with polyethylene glycol”
t0“Spinach”
Claim · model-written summary
Spinach RuBisCO prepared with ammonium sulfate showed a much larger decrease of activity in the linear phase.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- ammonium sulfatee0
- Outcome
- decrease of the activity in the linear phasee0
- Direction
- much largere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RuBisCO prepared with ammonium sulfate had a much larger decrease of the activity in the linear phase”
t0“Spinach”
Claim · model-written summary
The Euglena RuBisCO enzyme had a linear course of reaction with time for up to 20 minutes.
EuglenaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Euglena enzyme had a linear course of reaction with time for up to 20 minutes”
t0“Spinach”
Claim · model-written summary
The Km for CO2 of beforehand-activated spinach RuBisCO was 20 uM in the initial burst.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- Km for CO2e0
- Value
- 20 μMe0
- Qualifier
- initial burste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Km for CO2 of spinach RuBisCO activated beforehand was 20 μM in the initial burst, and 28 μM in the linear phase”
t0“Spinach”
Claim · model-written summary
The Km for CO2 of beforehand-activated spinach RuBisCO was 28 uM in the linear phase.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- Km for CO2e0
- Value
- 28 μMe0
- Qualifier
- linear phasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Km for CO2 of spinach RuBisCO activated beforehand was 20 μM in the initial burst, and 28 μM in the linear phase”
t0“Spinach”
Claim · model-written summary
The Km for CO2 in the linear phase of pre-inactivated spinach RuBisCO was 70 uM.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- Km for CO2e0
- Value
- 70 μMe0
- Qualifier
- pre-inactivated enzymee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Km for CO2 in the linear phase of the pre-inactivated enzyme was 70 μM”
t0“Spinach”
Claim · model-written summary
When the carboxylase reaction was initiated with inactive enzyme, activity was initially negligible and rose within 5 minutes to the level of the linear phase of the activated enzyme.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- activitye0
- Qualifier
- initiated with inactive enzymee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the carboxylase reaction initiated with inactive enzyme, the activity was initially negligible, but in 5 minutes increased to the level observed in the linear phase of the activated enzyme”
t0“Spinach”
Claim · model-written summary
The authors conclude that the RuBP concentration was the immediate cause of the two-phasic course of the spinach RuBisCO carboxylase reaction.
- Taxon
- SpinachSpinacia oleraceat0
- Compound
- RuBPe0
- Outcome
- two-phasic course of the carboxylase reactione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The concentration of RuBP was the immediate cause of the two-phasic course of the carboxylase reaction of spinach RuBisCO”
t0“Spinach”
Claim · model-written summary
The curvature of the time course was not observed below 35 uM RuBP.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- curvature of the time coursee0
- Qualifier
- below 35 μM RuBPe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The curvature of the time course was not observed below 35 μM RuBP”
t0“Spinach”
Claim · model-written summary
Spinach RuBisCO required over 88 uM RuBP for the conventional two-phasic course.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- conventional two-phasic coursee0
- Value
- 88 μMe0
- Qualifier
- over 88 μM RuBPe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The enzyme required over 88 μM RuBP for the conventional two-phasic course”
t0“Spinach”
Claim · model-written summary
Further increase of the RuBP concentration increased the extent of the curvature but did not make the curvature start sooner after the start of the reaction.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Further increase of the concentration of RuBPe0
- Outcome
- extent of the curvaturee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Further increase of the concentration of RuBP increased the extent of the curvature, but did not start the curvature sooner after the start of the reaction”
t0“Spinach”
Claim · model-written summary
In the linear phase, dilution of RuBP or its consumption to below 30 uM caused spinach RuBisCO to resume the biphasic reaction course after addition of a high RuBP concentration.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- resumed biphasic reaction coursee0
- Qualifier
- less than 30 μMe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Even if spinach RuBisCO was in the linear phase, dilution of RuBP or its consumption by the enzymatic reaction to less than 30 μM caused the enzyme to show the resumed biphasic reaction course after addition of a high concentration of RuBP”
t0“Spinach”