Abstract
Catalase is a major antioxidant enzyme located in plant peroxisomes that catalyzes the decomposition of H2O2. Based on our previous transcriptomic (RNA-Seq) and proteomic (iTRAQ) data at different stages of pepper (Capsicum annuum L.) fruit ripening and after exposure to nitric oxide (NO) enriched atmosphere, a broad analysis has allowed us to characterize the functioning of this enzyme. Three genes were identified, and their expression was differentially modulated during ripening and by NO gas treatment. A dissimilar behavior was observed in the protein expression of the encoded protein catalases (CaCat1-CaCat3). Total catalase activity was down-regulated by 50% in ripe (red) fruits concerning immature green fruits. This was corroborated by non-denaturing polyacrylamide gel electrophoresis, where only a single catalase isozyme was identified. In vitro analyses of the recombinant CaCat3 protein exposed to peroxynitrite (ONOO-) confirmed, by immunoblot assay, that catalase underwent a nitration process. Mass spectrometric analysis identified that Tyr348 and Tyr360 were nitrated by ONOO-, occurring near the active center of catalase. The data indicate the complex regulation at gene and protein levels of catalase during the ripening of pepper fruits, with activity significantly down-regulated in ripe fruits. Nitration seems to play a key role in this down-regulation, favoring an increase in H2O2 content during ripening. This pattern can be reversed by the exogenous NO application. While plant catalases are generally reported to be tetrameric, the analysis of the protein structure supports that pepper catalase has a favored quaternary homodimer nature. Taken together, data show that pepper catalase is down-regulated during fruit ripening, becoming a target of tyrosine nitration, which provokes its inhibition.
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Claims 11
Claim · model-written summary
Three pepper catalase genes were identified.
Verbatim
e0“Three genes were identified”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Catalase gene expression was differentially modulated during ripening and NO treatment.
Verbatim
e0“their expression was differentially modulated during ripening and by NO gas treatment”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
CaCat1 through CaCat3 protein expression showed dissimilar behavior.
Verbatim
e0“A dissimilar behavior was observed in the protein expression of the encoded protein catalases (CaCat1-CaCat3)”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Catalase activity was 50% lower in ripe red fruit than immature green fruit.
Verbatim
e0“Total catalase activity was down-regulated by 50% in ripe (red) fruits concerning immature green fruits”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Gel electrophoresis identified one catalase isozyme.
Verbatim
e0“only a single catalase isozyme was identified”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Peroxynitrite exposure nitrated recombinant CaCat3.
- Taxon
- peppere1
- Treatment
- peroxynitrite (ONOO-)e0
- Gene
- CaCat3e0
- Outcome
- catalase underwent a nitration processe0
Not reportedComparatorDirection
Verbatim
e0“recombinant CaCat3 protein exposed to peroxynitrite (ONOO-) confirmed, by immunoblot assay, that catalase underwent a nitration process”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Peroxynitrite nitrated Tyr348 near catalase active center.
- Taxon
- peppere1
- Treatment
- ONOO-e0
- Gene
- Tyr348e0
- Outcome
- Tyr348 and Tyr360 were nitratede0
- Qualifier
- near the active center of catalasee0
Not reportedComparatorDirection
Verbatim
e0“Tyr348 and Tyr360 were nitrated by ONOO-, occurring near the active center of catalase”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Peroxynitrite nitrated Tyr360 near catalase active center.
- Taxon
- peppere1
- Treatment
- ONOO-e0
- Gene
- Tyr360e0
- Outcome
- Tyr348 and Tyr360 were nitratede0
- Qualifier
- near the active center of catalasee0
Not reportedComparatorDirection
Verbatim
e0“Tyr348 and Tyr360 were nitrated by ONOO-, occurring near the active center of catalase”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Nitration was proposed to inhibit catalase and increase H2O2 during ripening.
Verbatim
e0“Nitration seems to play a key role in this down-regulation, favoring an increase in H2O2 content during ripening”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Exogenous NO could reverse the ripening pattern.
Not reportedComparator
Verbatim
e0“This pattern can be reversed by the exogenous NO application”
e1“pepper (Capsicum annuum L.) fruit ripening”
Claim · model-written summary
Pepper catalase structure favored a homodimer.
Verbatim
e0“pepper catalase has a favored quaternary homodimer nature”