Abstract
Recently, the uptake of 14C-labeled ascorbate (ASC) into highly purified bean (Phaseolus vulgaris L.) plasma membrane vesicles was demonstrated in our laboratory. However, the question of the redox status of the transported molecule (ASC or dehydroascorbate [DHA]) remained unanswered. In this paper we present evidence that DHA is transported through the plasma membrane. High-performance liquid chromatography analysis of the redox status of ASC demonstrated that freshly purified plasma membranes exhibit a high ASC oxidation activity. Although it is not yet clear whether this activity is enzymatic, it complicates the interpretation of ASC-transport experiments in vitro and in vivo. In an attempt to correlate the ASC redox status to transport of the molecule, the ability of different compounds to reduce DHA was analyzed and their effect on ASC-transport activity tested. Administering of various reductants resulted in different levels of inhibition of ASC uptake (dithiothreitol > dithioerythritol > [beta]-mercaptoethanol > [beta]-mercaptopropanol). Glutathione, cysteine, dithionite, and thiourea did not significantly affect ASC transport. Statistical analysis indicated a strong correlation of the Spearman rank correlation coefficient (Rs) of 0.919 (P = 0.0005, n = 9) between the level of ASC oxidation and the amount of transported molecules into the vesicles. The administering of ASC oxidants such as ferricyanide and ASC oxidase resulted in a stimulated ASC uptake into the plasma membrane vesicles. Together, our results demonstrate that a vitamin C carrier in purified bean plasma membranes translocates DHA from the apoplast to the cytosol.
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Claims 10
Claim · model-written summary
Freshly purified plasma membranes showed high ascorbate oxidation activity.
Verbatim
e0“freshly purified plasma membranes exhibit a high ASC oxidation activity”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Different reductants inhibited ascorbate uptake to differing degrees, ranked from dithiothreitol to mercaptopropanol.
- Taxon
- beane1
- Treatment
- various reductantse0
- Outcome
- ASC uptakee0
- Direction
- inhibitione0
- Qualifier
- dithiothreitol > dithioerythritol > [beta]-mercaptoethanol > [beta]-mercaptopropanole0
Not reportedComparator
Verbatim
e0“Administering of various reductants resulted in different levels of inhibition of ASC uptake (dithiothreitol > dithioerythritol > [beta]-mercaptoethanol > [beta]-mercaptopropanol)”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Glutathione did not significantly affect ascorbate transport.
Not reportedComparator
Verbatim
e0“Glutathione, cysteine, dithionite, and thiourea did not significantly affect ASC transport”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Cysteine did not significantly affect ascorbate transport.
Not reportedComparator
Verbatim
e0“Glutathione, cysteine, dithionite, and thiourea did not significantly affect ASC transport”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Dithionite did not significantly affect ascorbate transport.
Not reportedComparator
Verbatim
e0“Glutathione, cysteine, dithionite, and thiourea did not significantly affect ASC transport”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Thiourea did not significantly affect ascorbate transport.
Not reportedComparator
Verbatim
e0“Glutathione, cysteine, dithionite, and thiourea did not significantly affect ASC transport”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Ascorbate oxidation level strongly correlated with the amount transported into vesicles.
- Taxon
- beane1
- Compound
- ASCe0
- Outcome
- amount of transported molecules into the vesiclese0
- Value
- 0.919e0
- Qualifier
- P = 0.0005, n = 9e0
Not reportedDirection
Verbatim
e0“a strong correlation of the Spearman rank correlation coefficient (Rs) of 0.919 (P = 0.0005, n = 9) between the level of ASC oxidation and the amount of transported molecules into the vesicles”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Ferricyanide stimulated ascorbate uptake into plasma membrane vesicles.
Not reportedComparator
Verbatim
e0“The administering of ASC oxidants such as ferricyanide and ASC oxidase resulted in a stimulated ASC uptake into the plasma membrane vesicles”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
Ascorbate oxidase stimulated ascorbate uptake into plasma membrane vesicles.
Not reportedComparator
Verbatim
e0“The administering of ASC oxidants such as ferricyanide and ASC oxidase resulted in a stimulated ASC uptake into the plasma membrane vesicles”
e1“bean (Phaseolus vulgaris L.) plasma membrane vesicles”
Claim · model-written summary
The bean plasma membrane vitamin C carrier translocates dehydroascorbate from apoplast to cytosol.
Verbatim
e0“a vitamin C carrier in purified bean plasma membranes translocates DHA from the apoplast to the cytosol”
The same questions in other papers
cysteine · molecular: metabolites · Phaseolus vulgaris (common bean)Positive and negative results
1 in the opposite direction
- positive
glutathione · molecular: metabolites · Phaseolus vulgaris (common bean)Positive and negative results
4 in the opposite direction
- positive
- positive
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1 paper more in this group
See all 5 papers →ascorbate · nutrient: content · Phaseolus vulgaris (common bean)Results agree
2 papers in the same direction as this paper
- positive
- positive
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.