Abstract
The capacity of intact chloroplasts to synthesize long chain fatty acids from acetate depends on the stroma pH in Spinacia oleracea, U. S. hybrid 424. The pH optimum is close to 8.5. Lowering of the stroma pH leads to a reduction of acetate incorporation but does not suffice to eliminate fatty acid synthesis completely. Chain elongation from palmitic to oleic acid shows the same pH dependence. Fatty acid synthesis is activated in the dark upon the simultaneous addition of dihydroxyacetone phosphate and orthophosphate supplying ATP and oxaloacetate for reoxidation of NADPH in the stroma. Under these conditions both dark fatty acid synthesis and synthesis of oleate from palmitate show the same pH dependence as in the light. Dark fatty acid synthesis is further stimulated by increasing the stromal Mg(2+) concentration with the ionophore A 23187. In contrast to CO(2) fixation, dark fatty acid synthesis is considerably reduced by dithiothreitol (DTT). This observation may be due to an acetyl-CoA deficiency, caused by a nonenzymic acylation of DTT, and a competition for ATP between DTT-activated CO(2) fixation and fatty acid synthesis. Because d,l-glyceraldehyde as inhibitor of CO(2) fixation compensates the DTT effect on dark fatty acid synthesis, reducing equivalents may be involved in the light dependence of acetate activation.
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Claims 8
Claim · model-written summary
Spinach chloroplast fatty acid synthesis depends on stromal pH, with an optimum near 8.5.
- Taxon
- Spinacia oleracea
Spinacia oleraceae0 - Material
- U. S. hybrid 424e0
- Outcome
- synthesize long chain fatty acids from acetatee0
- Value
- 8.5e0
- Qualifier
- stroma pHe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The capacity of intact chloroplasts to synthesize long chain fatty acids from acetate depends on the stroma pH in Spinacia oleracea, U. S. hybrid 424. The pH optimum is close to 8.5.”
Claim · model-written summary
Lower stromal pH reduced acetate incorporation without eliminating fatty acid synthesis.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Lowering of the stroma pHe0
- Outcome
- acetate incorporatione0
- Direction
- reductione0
- Qualifier
- does not suffice to eliminate fatty acid synthesis completelye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lowering of the stroma pH leads to a reduction of acetate incorporation but does not suffice to eliminate fatty acid synthesis completely.”
t0“Spinach”
Claim · model-written summary
Elongation of palmitic to oleic acid had the same pH dependence.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- Chain elongation from palmitic to oleic acide0
- Qualifier
- same pH dependencee0
Not reportedMaterialGeneCompoundOrgan / stageInteractorTreatmentComparatorSettingDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chain elongation from palmitic to oleic acid shows the same pH dependence.”
t0“Spinach”
Claim · model-written summary
Dihydroxyacetone phosphate and orthophosphate together activated fatty acid synthesis in the dark.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- simultaneous addition of dihydroxyacetone phosphate and orthophosphatee0
- Outcome
- Fatty acid synthesise0
- Direction
- activatede0
- Qualifier
- in the darke0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fatty acid synthesis is activated in the dark upon the simultaneous addition of dihydroxyacetone phosphate and orthophosphate”
t0“Spinach”
Claim · model-written summary
Dark fatty acid synthesis and oleate synthesis from palmitate showed the same pH dependence as in light.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- dark fatty acid synthesis and synthesis of oleate from palmitatee0
- Qualifier
- same pH dependence as in the lighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both dark fatty acid synthesis and synthesis of oleate from palmitate show the same pH dependence as in the light”
t0“Spinach”
Claim · model-written summary
Increasing stromal magnesium with A 23187 further stimulated dark fatty acid synthesis.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- increasing the stromal Mg(2+) concentration with the ionophore A 23187e0
- Outcome
- Dark fatty acid synthesise0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dark fatty acid synthesis is further stimulated by increasing the stromal Mg(2+) concentration with the ionophore A 23187.”
t0“Spinach”
Claim · model-written summary
DTT considerably reduced dark fatty acid synthesis.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- dithiothreitol (DTT)e0
- Outcome
- dark fatty acid synthesise0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dark fatty acid synthesis is considerably reduced by dithiothreitol (DTT)”
t0“Spinach”
Claim · model-written summary
Glyceraldehyde compensated the DTT effect on dark fatty acid synthesis.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- d,l-glyceraldehydee0
- Outcome
- DTT effect on dark fatty acid synthesise0
- Direction
- compensatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“d,l-glyceraldehyde as inhibitor of CO(2) fixation compensates the DTT effect on dark fatty acid synthesis”
t0“Spinach”
The same questions in other papers
ph · molecular: metabolites · Spinacia oleracea (spinach)Positive and negative results
3 papers in the same direction as this paper · 3 in the opposite direction
- positive
- positive
- positive
3 papers more in this group
See all 7 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.