Abstract
Photosystem II (PSII) membranes exhibit catalase and polyphenol oxidase (PPO) activities. Mild heat treatment of PSII membranes for 90 min at 30 degrees C releases most of these enzyme activities into the supernatant, accompanied by a 7-fold activation of PPO. In contrast, mild heat treatment of thylakoid membranes does not release significant amounts of either activity, indicating that both enzymes are bound to the luminal surface of the thylakoid membrane. The heat-released PSII membrane-associated catalase and PPO have been purified and characterized. Catalase activity was correlated with a 63 kDa polypeptide which was purified by batch adsorption to anion-exchange beads followed by gel filtration. The PSII membrane-associated catalase is unstable in solution, probably due to irreversible aggregation. The enzyme was characterized in terms of molecular and subunit size, amino-acid composition, UV-visible absorption, heme content, pH optimum, inhibitor sensitivity, and K(m) value for H2O2. Its properties indicate that the PSII membrane-associated catalase is a luminal thylakoid membrane-bound heme enzyme that has not been identified previously. The residual catalase activity of PSII membranes after mild heat treatment is irreversibly inhibited with 3-amino-1,2,4-triazole, a specific inhibitor of heme catalases, without inhibition of O2-evolution activity. This result indicates that little, if any, of the catalase activity from PSII membranes in the dark is catalyzed by the O2-evolving center of PSII. PPO activity was correlated with a 48 kDa polypeptide. However, the 48 kDa polypeptide and another heat-released polypeptide of 72 kDa have the same N-terminal sequence, which is also identical to that of a known 64 kDa protein [Hind, G., Marshak, D. R., & Coughlan, S. J. (1995) Biochemistry 34, 8157-8164]. During heat treatment of PSII membranes and further manipulations it was found that the 72 kDa polypeptide was largely converted into the 48 kDa polypeptide. Thus, the 72 kDa polypeptide appears to be a latent precursor of the active 48 kDa PPO. The PSII membrane-associated PPO was purified by anion-exchange chromatography and was characterized in terms of substrate specificity, pH optimum, inhibitor sensitivity and native molecular weight. The heat-released PPO appears to be identical to the enzyme previously isolated from spinach thylakoid membranes [Golbeck, J. H., & Cammarata, K. V. (1981) Plant Physiol. 67, 977-984].
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Claims 16
Claim · model-written summary
PSII membranes showed catalase and PPO activities.
- Taxon
- Spinach
Spinacia oleraceat0 - Outcome
- catalase and polyphenol oxidase (PPO) activitiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“Photosystem II (PSII) membranes exhibit catalase and polyphenol oxidase (PPO) activities.”
Claim · model-written summary
Mild heating of PSII membranes released most catalase and PPO activities.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Mild heat treatment of PSII membranes for 90 min at 30 degrees Ce0
- Outcome
- these enzyme activitiese0
- Direction
- releasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“Mild heat treatment of PSII membranes for 90 min at 30 degrees C releases most of these enzyme activities into the supernatant”
Claim · model-written summary
Mild heating activated PPO sevenfold.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Mild heat treatment of PSII membranes for 90 min at 30 degrees Ce1
- Outcome
- PPOe0
- Direction
- activatione0
- Value
- 7-folde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“accompanied by a 7-fold activation of PPO”
e1“Mild heat treatment of PSII membranes for 90 min at 30 degrees C”
Claim · model-written summary
Mild heating did not release significant amounts of either activity from thylakoid membranes.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- mild heat treatment of thylakoid membranese0
- Outcome
- either activitye0
- Direction
- does not releasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“mild heat treatment of thylakoid membranes does not release significant amounts of either activity”
Claim · model-written summary
Both enzymes were inferred to bind the luminal thylakoid surface.
- Taxon
- SpinachSpinacia oleraceat0
- Organ / stage
- thylakoid membranee0
- Outcome
- bound to the luminal surface of the thylakoid membranee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“both enzymes are bound to the luminal surface of the thylakoid membrane”
Claim · model-written summary
Catalase activity correlated with a 63 kDa polypeptide.
- Taxon
- SpinachSpinacia oleraceat0
- Gene
- 63 kDa polypeptidee0
- Outcome
- Catalase activitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“Catalase activity was correlated with a 63 kDa polypeptide”
Claim · model-written summary
PSII-associated catalase was unstable in solution, probably through irreversible aggregation.
- Taxon
- SpinachSpinacia oleraceat0
- Gene
- catalasee0
- Outcome
- unstable in solutione0
- Qualifier
- probably due to irreversible aggregatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“The PSII membrane-associated catalase is unstable in solution, probably due to irreversible aggregation”
Claim · model-written summary
PSII-associated catalase was characterized as a previously unidentified luminal membrane-bound heme enzyme.
- Taxon
- SpinachSpinacia oleraceat0
- Gene
- catalasee0
- Outcome
- luminal thylakoid membrane-bound heme enzyme that has not been identified previouslye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“PSII membrane-associated catalase is a luminal thylakoid membrane-bound heme enzyme that has not been identified previously”
Claim · model-written summary
3-amino-1,2,4-triazole irreversibly inhibited residual catalase activity after heating.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- 3-amino-1,2,4-triazolee0
- Outcome
- residual catalase activity of PSII membranese0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“The residual catalase activity of PSII membranes after mild heat treatment is irreversibly inhibited with 3-amino-1,2,4-triazole”
Claim · model-written summary
3-amino-1,2,4-triazole did not inhibit oxygen evolution.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- 3-amino-1,2,4-triazolee1
- Outcome
- O2-evolution activitye0
- Direction
- without inhibitione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“without inhibition of O2-evolution activity”
e1“3-amino-1,2,4-triazole”
Claim · model-written summary
The oxygen-evolving center contributed little, if any, dark catalase activity.
- Taxon
- SpinachSpinacia oleraceat0
- Outcome
- catalase activity from PSII membranes in the darke0
- Qualifier
- O2-evolving center of PSIIe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“little, if any, of the catalase activity from PSII membranes in the dark is catalyzed by the O2-evolving center of PSII”
Claim · model-written summary
PPO activity correlated with a 48 kDa polypeptide.
- Taxon
- SpinachSpinacia oleraceat0
- Gene
- 48 kDa polypeptidee0
- Outcome
- PPO activitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“PPO activity was correlated with a 48 kDa polypeptide”
Claim · model-written summary
The 48 and 72 kDa polypeptides shared an N-terminal sequence identical to a known 64 kDa protein.
- Taxon
- SpinachSpinacia oleraceat0
- Gene
- 48 kDa polypeptidee0
- Outcome
- same N-terminal sequencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“the 48 kDa polypeptide and another heat-released polypeptide of 72 kDa have the same N-terminal sequence, which is also identical to that of a known 64 kDa protein”
Claim · model-written summary
Most 72 kDa polypeptide converted into the 48 kDa polypeptide during heating and manipulation.
- Taxon
- SpinachSpinacia oleraceat0
- Gene
- 72 kDa polypeptidee0
- Outcome
- converted into the 48 kDa polypeptidee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“the 72 kDa polypeptide was largely converted into the 48 kDa polypeptide”
Claim · model-written summary
The 72 kDa polypeptide was interpreted as a latent precursor of active PPO.
- Taxon
- SpinachSpinacia oleraceat0
- Gene
- 72 kDa polypeptidee0
- Outcome
- latent precursor of the active 48 kDa PPOe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Spinach”
e0“the 72 kDa polypeptide appears to be a latent precursor of the active 48 kDa PPO”
Claim · model-written summary
Heat-released PPO appeared identical to an enzyme previously isolated from spinach thylakoids.
- Taxon
- spinachSpinacia oleraceae0
- Gene
- PPOe0
- Outcome
- identical to the enzyme previously isolated from spinach thylakoid membranese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The heat-released PPO appears to be identical to the enzyme previously isolated from spinach thylakoid membranes”