Abstract
A study was made to determine conditions under which malate oxidation rates in corn (Zea mays L.) mitochondria are limited by transport processes. In the absence of added ADP, inorganic phosphate increased malate oxidation rates by processes inhibited by mersalyl and oligomycin, but phosphate did not stimulate uncoupled respiration. However, the uncoupled oxidation rates were inhibited by butylmalonate and mersalyl. When uncoupler was added prior to substrate, subsequent O(2) uptake rates were reduced when malate and succinate, but not exogenous NADH, were used. Uncoupler and butylmalonate also inhibited swelling in malate solutions and malate accumulation by these mitochondria, which were found to have a high endogenous phosphate content. Addition of uncoupler after malate or succinate produced an initial rapid oxidation which declined as the mitochondria lost solute and contracted. This decline was not affected by addition of ADP or AMP, and was not observed when exogenous NADH was substrate. Increasing K(+) permeability with valinomycin increased the P-trifluoromethoxy (carboxylcyanide)phenyl hydrazone inhibition. Kinetic studies showed the slow rate of malate oxidation in the presence of uncoupler to be characterized by a high Km and a low V(max), probably reflecting a diffusion-limited process.The results indicate that rapid malate and succinate oxidation require the operation of both the phosphate and dicarboxylate transporters, which in turn depend on maintenance of a proton motive force across the inner membrane. In addition, phosphate can stimulate acceptorless malate oxidation by reaction with the coupling mechanism, and in uncoupled mitochondria which are depleted of substrate there is a slow rate of oxidation which appears to be limited by diffusive entry.
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Claims 19
Claim · model-written summary
Without added ADP, inorganic phosphate increased malate oxidation rates.
- Taxon
- corn
Zea mays subsp. mayse1 - Organ / stage
- mitochondriae1
- Treatment
- inorganic phosphatee0
- Outcome
- malate oxidation ratese0
- Direction
- increasede0
- Comparator
- absence of added ADPe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the absence of added ADP, inorganic phosphate increased malate oxidation rates”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Mersalyl inhibited phosphate-stimulated malate oxidation.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- mersalyle0
- Outcome
- malate oxidation ratese0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inorganic phosphate increased malate oxidation rates by processes inhibited by mersalyl and oligomycin”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Oligomycin inhibited phosphate-stimulated malate oxidation.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- oligomycine0
- Outcome
- malate oxidation ratese0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inorganic phosphate increased malate oxidation rates by processes inhibited by mersalyl and oligomycin”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Phosphate did not stimulate uncoupled respiration.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- phosphatee0
- Outcome
- uncoupled respiratione0
- Direction
- did not stimulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“phosphate did not stimulate uncoupled respiration”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
butylmalonate inhibited uncoupled oxidation.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- butylmalonatee0
- Outcome
- uncoupled oxidation ratese0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the uncoupled oxidation rates were inhibited by butylmalonate and mersalyl”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
mersalyl inhibited uncoupled oxidation.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- mersalyle0
- Outcome
- uncoupled oxidation ratese0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the uncoupled oxidation rates were inhibited by butylmalonate and mersalyl”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Uncoupler added before malate reduced subsequent oxygen uptake.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- uncouplere0
- Outcome
- O(2) uptake ratese0
- Direction
- reducede0
- Qualifier
- malatee0
- Comparator
- exogenous NADHe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When uncoupler was added prior to substrate, subsequent O(2) uptake rates were reduced when malate and succinate, but not exogenous NADH, were used”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Uncoupler added before succinate reduced subsequent oxygen uptake.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- uncouplere0
- Outcome
- O(2) uptake ratese0
- Direction
- reducede0
- Qualifier
- succinatee0
- Comparator
- exogenous NADHe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When uncoupler was added prior to substrate, subsequent O(2) uptake rates were reduced when malate and succinate, but not exogenous NADH, were used”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Uncoupler inhibited mitochondrial swelling and malate accumulation.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- Uncouplere0
- Outcome
- swelling in malate solutions and malate accumulatione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Uncoupler and butylmalonate also inhibited swelling in malate solutions and malate accumulation by these mitochondria”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
butylmalonate inhibited mitochondrial swelling and malate accumulation.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- butylmalonatee0
- Outcome
- swelling in malate solutions and malate accumulatione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Uncoupler and butylmalonate also inhibited swelling in malate solutions and malate accumulation by these mitochondria”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Uncoupler after malate caused rapid initial oxidation followed by decline as mitochondria contracted.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- uncouplere0
- Outcome
- oxidatione0
- Direction
- declinede0
- Qualifier
- malatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Addition of uncoupler after malate or succinate produced an initial rapid oxidation which declined as the mitochondria lost solute and contracted”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Uncoupler after succinate caused rapid initial oxidation followed by decline as mitochondria contracted.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- uncouplere0
- Outcome
- oxidatione0
- Direction
- declinede0
- Qualifier
- succinatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Addition of uncoupler after malate or succinate produced an initial rapid oxidation which declined as the mitochondria lost solute and contracted”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
ADP or AMP addition did not alter the oxidation decline.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- ADP or AMPe0
- Outcome
- declinee0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This decline was not affected by addition of ADP or AMP”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Exogenous NADH did not show the oxidation decline.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- exogenous NADHe0
- Outcome
- declinee0
- Direction
- not observede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This decline was not affected by addition of ADP or AMP, and was not observed when exogenous NADH was substrate”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Valinomycin increased inhibition by P-trifluoromethoxy (carboxylcyanide)phenyl hydrazone.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- valinomycine0
- Outcome
- P-trifluoromethoxy (carboxylcyanide)phenyl hydrazone inhibitione0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increasing K(+) permeability with valinomycin increased the P-trifluoromethoxy (carboxylcyanide)phenyl hydrazone inhibition”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Malate oxidation with uncoupler had a high Km and low V(max), consistent with diffusion limitation.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- uncouplere0
- Outcome
- rate of malate oxidatione0
- Direction
- slowe0
- Qualifier
- diffusion-limited processe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“slow rate of malate oxidation in the presence of uncoupler to be characterized by a high Km and a low V(max), probably reflecting a diffusion-limited process”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Rapid malate and succinate oxidation require phosphate and dicarboxylate transporters and proton motive force.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Outcome
- rapid malate and succinate oxidatione0
- Qualifier
- proton motive force across the inner membranee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rapid malate and succinate oxidation require the operation of both the phosphate and dicarboxylate transporters, which in turn depend on maintenance of a proton motive force across the inner membrane”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Phosphate may stimulate malate oxidation through the coupling mechanism.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Treatment
- phosphatee0
- Outcome
- acceptorless malate oxidatione0
- Direction
- stimulatee0
- Qualifier
- coupling mechanisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“phosphate can stimulate acceptorless malate oxidation by reaction with the coupling mechanism”
e1“corn (Zea mays L.) mitochondria”
Claim · model-written summary
Slow oxidation in uncoupled substrate-depleted mitochondria appears limited by diffusive entry.
- Taxon
- cornZea mays subsp. mayse1
- Organ / stage
- mitochondriae1
- Outcome
- slow rate of oxidatione0
- Qualifier
- diffusive entrye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in uncoupled mitochondria which are depleted of substrate there is a slow rate of oxidation which appears to be limited by diffusive entry”
e1“corn (Zea mays L.) mitochondria”
The same questions in other papers
oligomycin · molecular: metabolites · Zea mays (maize)Results agree
3 papers in the same direction as this paper
- negative
- no effect
- negative
phosphorus · physiology: respiration · Zea mays (maize)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
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.