Abstract
Uptake of d, l-glycerate into the chloroplast stroma has been studied using the technique of silicone oil filtering centrifugation. Glycerate uptake was 3 to 5 times higher in the light than in darkness, the stimulation by light being abolished by the proton ionophore carbonyl cyanide p-trifluoromethoxyphenyl hydrazone. The pH optimum for uptake was 7.0 at 2 degrees C and 8.5 at 20 degrees C, but at all pH values the rate of uptake was higher at 20 degrees C than at 2 degrees C. Uptake was concentration dependent, saturating above 8 millimolar glycerate. At 2 degrees C, the K(m) was 0.3 millimolar and the V(max) was 13 micromoles per milligram of chlorophyll per hour. At 20 degrees C initial rates of glycerate uptake were higher than 40 micromoles per milligram of chlorophyll per hour.Although there was some metabolism of glycerate by chloroplasts in the light, even at 2C, the actual concentration of glycerate in the stroma, determined by chromatography, was 2 to 4 times that in the incubation medium. NH(4)Cl stimulated glycerate uptake and decreased its metabolism by the chloroplasts resulting in stromal concentrations of glycerate up to 6 times higher than in the medium. A number of weak acids inhibited glycerate uptake, lactate and glyoxylate being the most effective. The inhibition was not competitive with respect to glycerate. Glycerate uptake was also inhibited by p-chloromercuriphenyl sulfonate.Substrates of the dicarboxylate transporter did not inhibit glycerate uptake. Of the four substrates of the phosphate transporter tested, 3-phosphoglycerate and dihydroxyacetone phosphate inhibited glycerate uptake but orthophosphate and glyceraldehyde-3-phosphate had little effect. The inhibition by 3-phosphoglycerate was competitive with respect to glycerate, with a K(i) of 0.2 millimolar, suggesting that 3-phosphoglycerate binds to the same site as glycerate. However, glycerate only inhibited 3-phosphoglycerate uptake slightly and the inhibition was not competitive, indicating that glycerate does not bind to the phosphate transporter. Glycerate did not counter exchange with (32)P in chloroplasts which had been preloaded with (32)Pi, confirming that glycerate did not enter via the phosphate transporter.The results suggest that the chloroplast envelope contains a specific glycerate transporter, which differs from the previously reported transporters in that it is stimulated by light.
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Claims 20
Claim · model-written summary
Glycerate uptake was three to five times higher in light than darkness.
- Taxon
- Spinach
Spinacia oleraceat0 - Treatment
- lighte0
- Outcome
- Glycerate uptakee0
- Direction
- highere0
- Value
- 3 to 5 timese0
- Comparator
- darknesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“Glycerate uptake was 3 to 5 times higher in the light than in darkness”
Claim · model-written summary
A proton ionophore abolished the stimulation of uptake by light.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- carbonyl cyanide p-trifluoromethoxyphenyl hydrazonee0
- Outcome
- stimulation by lighte0
- Direction
- abolishede0
- Comparator
- lighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“the stimulation by light being abolished by the proton ionophore carbonyl cyanide p-trifluoromethoxyphenyl hydrazone”
Claim · model-written summary
The pH optimum for uptake was 7.0 at 2 degrees C.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- pH optimum for uptakee0
- Value
- 7.0e0
- Qualifier
- 2 degrees Ce0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“The pH optimum for uptake was 7.0 at 2 degrees C”
Claim · model-written summary
The pH optimum for uptake was 8.5 at 20 degrees C.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- 8.5e0
- Value
- 8.5e0
- Qualifier
- 20 degrees Ce0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“8.5 at 20 degrees C”
Claim · model-written summary
Glycerate uptake was higher at 20 degrees C than at 2 degrees C at all pH values.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- 20 degrees Ce0
- Outcome
- rate of uptakee0
- Direction
- highere0
- Comparator
- 2 degrees Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“at all pH values the rate of uptake was higher at 20 degrees C than at 2 degrees C”
Claim · model-written summary
Uptake saturated above 8 millimolar glycerate.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- Uptakee0
- Direction
- saturatinge0
- Value
- 8 millimolar glyceratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“Uptake was concentration dependent, saturating above 8 millimolar glycerate”
Claim · model-written summary
At 2 degrees C, uptake K(m) was 0.3 millimolar.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- K(m)e0
- Value
- 0.3 millimolare0
- Qualifier
- 2 degrees Ce0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“At 2 degrees C, the K(m) was 0.3 millimolar”
Claim · model-written summary
At 2 degrees C, V(max) was 13 micromoles per milligram of chlorophyll per hour.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- V(max)e0
- Value
- 13 micromoles per milligram of chlorophyll per houre0
- Qualifier
- 2 degrees Ce1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“the V(max) was 13 micromoles per milligram of chlorophyll per hour”
e1“At 2 degrees C”
Claim · model-written summary
At 20 degrees C initial glycerate uptake exceeded 40 micromoles per milligram of chlorophyll per hour.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- initial rates of glycerate uptakee0
- Direction
- highere0
- Value
- 40 micromoles per milligram of chlorophyll per houre0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“At 20 degrees C initial rates of glycerate uptake were higher than 40 micromoles per milligram of chlorophyll per hour”
Claim · model-written summary
Some glycerate was metabolized by chloroplasts in the light even at 2C.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- metabolism of glycerate by chloroplastse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“there was some metabolism of glycerate by chloroplasts in the light, even at 2C”
Claim · model-written summary
Stromal glycerate concentration was two to four times that in incubation medium.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- concentration of glycerate in the stromae0
- Direction
- higherinferrede0
- Value
- 2 to 4 timese0
- Qualifier
- determined by chromatographye0
- Comparator
- incubation mediume0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“concentration of glycerate in the stroma, determined by chromatography, was 2 to 4 times that in the incubation medium”
Claim · model-written summary
NH(4)Cl stimulated glycerate uptake.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- NH(4)Cle0
- Outcome
- glycerate uptakee0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“NH(4)Cl stimulated glycerate uptake”
Claim · model-written summary
NH(4)Cl decreased glycerate metabolism by chloroplasts.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- NH(4)Cle0
- Outcome
- metabolism by the chloroplastse0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“NH(4)Cl stimulated glycerate uptake and decreased its metabolism by the chloroplasts”
Claim · model-written summary
NH(4)Cl produced stromal glycerate concentrations up to six times medium concentrations.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- NH(4)Cle1
- Outcome
- stromal concentrations of glyceratee0
- Direction
- highere0
- Value
- 6 timese0
- Comparator
- mediume0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“stromal concentrations of glycerate up to 6 times higher than in the medium”
e1“NH(4)Cl stimulated glycerate uptake”
Claim · model-written summary
Weak acids inhibited uptake, with lactate and glyoxylate most effective.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- weak acidse0
- Outcome
- glycerate uptakee0
- Direction
- inhibitede0
- Qualifier
- lactate and glyoxylate being the most effectivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“A number of weak acids inhibited glycerate uptake, lactate and glyoxylate being the most effective”
Claim · model-written summary
Weak acid inhibition was noncompetitive with glycerate.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- inhibition was not competitive with respect to glyceratee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“The inhibition was not competitive with respect to glycerate”
Claim · model-written summary
p-chloromercuriphenyl sulfonate inhibited glycerate uptake.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- p-chloromercuriphenyl sulfonatee0
- Outcome
- Glycerate uptakee0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“Glycerate uptake was also inhibited by p-chloromercuriphenyl sulfonate”
Claim · model-written summary
Dicarboxylate transporter substrates did not inhibit glycerate uptake.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Substrates of the dicarboxylate transportere0
- Outcome
- glycerate uptakee0
- Direction
- did not inhibite0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“Substrates of the dicarboxylate transporter did not inhibit glycerate uptake”
Claim · model-written summary
3-phosphoglycerate and dihydroxyacetone phosphate inhibited glycerate uptake.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- 3-phosphoglycerate and dihydroxyacetone phosphatee0
- Outcome
- glycerate uptakee0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“3-phosphoglycerate and dihydroxyacetone phosphate inhibited glycerate uptake”
Claim · model-written summary
Orthophosphate and glyceraldehyde-3-phosphate had little effect on glycerate uptake.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- orthophosphate and glyceraldehyde-3-phosphatee0
- Outcome
- glycerate uptakee1
- Direction
- little effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach Chloroplasts”
e0“orthophosphate and glyceraldehyde-3-phosphate had little effect”
e1“inhibited glycerate uptake but orthophosphate”
The same questions in other papers
dihydroxyacetone phosphate · nutrient: content · Spinacia oleracea (spinach)Positive and negative results
1 in the opposite direction
- positive
sulfonate · nutrient: content · Spinacia oleracea (spinach)Results agree
1 paper in the same direction as this paper
- negative
ammonium chloride · molecular: metabolites · Spinacia oleracea (spinach)Results agree
3 papers in the same direction as this paper
- positive
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growing medium · nutrient: content · Spinacia oleracea (spinach)Positive and negative results
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See all 6 papers →light · nutrient: content · Spinacia oleracea (spinach)Positive and negative results
4 papers in the same direction as this paper · 3 in the opposite direction
- negative
- negative
- negative
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See all 8 papers →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.