CAT2 (CATALASE2, At4g35090) encodes the major leaf catalase of Arabidopsis, a heme-containing monofunctional catalase that disproportionates hydrogen peroxide to water and O2. It accounts for most leaf catalase activity and acts mainly as a tetramer in the peroxisomal matrix, where it removes the H2O2 generated by glycolate oxidase in the photorespiratory C2 cycle; a cytosolic pool is folded and activated by the chaperone NCA1 before or during peroxisomal import. cat2 knockouts are conditional photorespiratory mutants: in air they show reduced rosette growth, intracellular redox perturbation, activation of oxidative and salicylic acid-dependent signalling and day length-dependent lesions, all suppressed by high CO2 and attenuated by loss of GOX1. CAT2 is therefore the main sink for photorespiratory H2O2 and a key regulator of intracellular H2O2-dependent stress signalling. Its expression is light-stimulated and circadian, and it is also induced by several abiotic stresses.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004096 catalase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of catalase activity across the monofunctional catalase family. Reason: Core function. CAT2 (At4g35090) is itself among the experimental sources of this PAINT node, reflecting its own mutant evidence; catalase activity is conserved across the monofunctional heme catalases. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Belongs to the catalase family. PMID:25700484 deletion of CAT2 reduces catalase activity by 80% PMID:25700484 the size of a CAT2 tetramer) had the highest activity in our assay |
| GO:0004096 catalase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined automated annotation (InterPro/EC/Rhea) to catalase activity. Reason: Agrees with experimental data on CAT2 activity. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Belongs to the catalase family. PMID:25700484 the size of a CAT2 tetramer) had the highest activity in our assay |
| GO:0004096 catalase activity | IMP PMID:15200641 Catalase deficiency drastically affects gene expression indu... | ACCEPT | Summary: Catalase-deficient transgenic Arabidopsis lines with reduced peroxisomal catalase activity were used to study photorespiratory H2O2 responses under high light. Reason: Cached text is abstract-only and does not name the silenced gene, but CAT2 provides about 80% of leaf catalase activity (PMID:25700484), and the curator, who read the full text, attributed the loss of activity to CAT2. Accepted, deferring to the curator. Supporting Evidence: PMID:15200641 Reduced peroxisomal catalase activity increased sensitivity toward both ozone and photorespiratory H(2)O(2)-induced cell death in transgenic catalase-deficient Arabidopsis thaliana. PMID:15200641 Because catalases are the major H(2)O(2) scavengers that remove the bulk of cellular H(2)O(2), altering their levels allows in planta modulation of H(2)O(2) concentrations. PMID:25700484 deletion of CAT2 reduces catalase activity by 80% |
| GO:0004096 catalase activity | IMP PMID:20452979 The in vivo toxicity of hydroxyurea depends on its direct ta... | ACCEPT | Summary: Hydroxyurea-resistant EMS mutants map to CATALASE2 and all show significantly reduced catalase activity. Reason: Seventeen independent cat2 alleles identified by forward genetics reduce catalase activity, including missense alleles; directly links CAT2 to catalase activity. Biochemical activity of recombinant CAT2 (PMID:25700484) confirms it. Supporting Evidence: PMID:20452979 identified a point mutation in the CATALASE2 gene (AT4G35090) PMID:20452979 When compared with the wild type, all mutants displayed a significant decrease (95% confidence level) in catalase activity PMID:25700484 the size of a CAT2 tetramer) had the highest activity in our assay |
| GO:0005515 protein binding | IPI PMID:14581623 Arabidopsis NDK1 is a component of ROS signaling by interact... | REMOVE | Summary: Yeast two-hybrid interaction of NDK1 with CAT2 (and CAT1, CAT3). Reason: Bare protein binding is uninformative. The NDK1 interaction was detected by yeast two-hybrid (abstract-only cache), and no more specific molecular function of CAT2 follows from it. Removal does not mean the interaction is false. Supporting Evidence: PMID:14581623 Interactions between AtNDK1-AtCAT1 and AtNDK1-AtCAT2 were also detected with the two-hybrid system. |
| GO:0005515 protein binding | IPI PMID:19452453 Proteomic profiling of tandem affinity purified 14-3-3 prote... | REMOVE | Summary: CAT2 co-purified with TAP-tagged 14-3-3 omega in a proteomic screen for 14-3-3 clients. Reason: Bare protein binding from a high-throughput TAP-MS client screen is uninformative and does not define a specific molecular function of CAT2 (the abstract lists 121 putative clients). Removal does not mean the interaction is false. Supporting Evidence: PMID:19452453 The identification here of 121 putative clients provides support for in vivo 14-3-3 interactions with a diverse array of proteins |
| GO:0005634 nucleus | ISM GO_REF:0000122 | REMOVE | Summary: AtSubP sequence-based prediction of nuclear location. Reason: Computational prediction only. CAT2 localizes to peroxisomes (GFP, PMID:25700484) with a cytosolic pool bound by NCA1; no experimental study reports nuclear CAT2 or a nuclear role, and UniProt lists only cytosol and peroxisome matrix. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | MODIFY | Summary: Phylogenetic inference that CAT2 is active in the cytoplasm. Reason: Correct but general: both supported locations, the peroxisomal matrix (GFP, PMID:25700484) and the cytosol (NCA1 BiFC, PMID:25700484), are part of the cytoplasm. Replace with these specific terms, both already carried by the gene. Propagation Review Root cause: NO FAILURE NON CORE Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000157250 · PTN000157250 SUPPORTS TRANSFER Deep catalase node; cytoplasm is correct for CAT2 (peroxisomal matrix and cytosolic pool, PMID:25700484) but less specific than the experimentally supported compartments. AGI_LocusCode:AT4G35090 · CAT2 SUPPORTS TRANSFER The target itself is among the experimental sources, as expected for a gene with its own localization data. Proposed replacements: peroxisomal matrix cytosol Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 PMID:25700484 NCA1 colocalizes and interacts with CAT2 in cytosol |
| GO:0005739 mitochondrion | HDA PMID:14671022 Experimental analysis of the Arabidopsis mitochondrial prote... | MARK AS OVER ANNOTATED | Summary: Detected in an LC-MS/MS survey of the Arabidopsis mitochondrial proteome. Reason: CAT2 is a soluble peroxisomal matrix enzyme (GFP localization, PMID:25700484) and one of the most abundant leaf peroxisomal proteins. Detection in a bulk organelle or fraction proteome of this kind is most simply explained by carry-over of peroxisomes or released matrix protein, and no targeted study shows a functional CAT2 pool in this compartment. The detection is not contradicted, but it does not describe where CAT2 acts. Action follows the ARATH convention for single high-throughput proteomics location hits (projects/ARATH/organelle-audit.md, rule 3). CAT2 has no mitochondrial presequence and the study notes that only about half of its proteins are predicted to be mitochondrial. Supporting Evidence: PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 |
| GO:0005777 peroxisome | HDA PMID:17951448 Proteome analysis of Arabidopsis leaf peroxisomes reveals no... | MODIFY | Summary: Identified in the proteome of purified Arabidopsis leaf peroxisomes. Reason: Correct, but the more specific peroxisomal matrix (GO:0005782) is supported for CAT2 (GFP, PMID:25700484; UniProt) and is already carried by the gene. CAT2 is a soluble matrix enzyme. Proposed replacements: peroxisomal matrix Supporting Evidence: PMID:17951448 Catalase isoform 3 (CAT3; At1g20620; 80% identical with CAT1 and 2) was more prominent on the two-dimensional gel than CAT2 (At4g35090) file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. |
| GO:0005777 peroxisome | IBA GO_REF:0000033 | MODIFY | Summary: Phylogenetic inference that CAT2 is active in the peroxisome. Reason: Correct; refine to peroxisomal matrix (GO:0005782), which CAT2 already carries by EXP and IEA. Propagation Review Root cause: NO FAILURE CORE Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000157342 · PTN000157342 SUPPORTS TRANSFER Plant catalase node; peroxisome is correct for CAT2 and the refinement to peroxisomal matrix is only a granularity change. AGI_LocusCode:AT4G35090 · CAT2 SUPPORTS TRANSFER The target itself is among the experimental sources of the node. Proposed replacements: peroxisomal matrix Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 |
| GO:0005782 peroxisomal matrix | EXP PMID:25700484 A chaperone function of NO CATALASE ACTIVITY1 is required to... | ACCEPT | Summary: CAT2-GFP localizes predominantly to peroxisomes in Col-0 and nca1-3. Reason: Core location. Catalase is a soluble matrix enzyme that removes H2O2 from peroxisomal oxidases; UniProt records peroxisome matrix from this paper. Supporting Evidence: PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. |
| GO:0005782 peroxisomal matrix | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location (Peroxisome matrix) mapped to GO. Reason: Based on the experimental UniProt location from PMID:25700484. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. |
| GO:0005829 cytosol | HDA PMID:25293756 A proteomic strategy for global analysis of plant protein co... | KEEP AS NON CORE | Summary: Detected in a size-exclusion chromatography/proteomic survey of soluble protein complexes. Reason: A cytosolic CAT2 pool is supported independently: NCA1 interacts with CAT2 in the cytosol (BiFC) and UniProt records cytosol from PMID:25700484. The cytosolic pool relates to folding and activation before or during import rather than the main site of action, so it is non-core. Supporting Evidence: PMID:25700484 NCA1 colocalizes and interacts with CAT2 in cytosol file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. |
| GO:0005829 cytosol | RCA NOT PMID:21166475 Analysis of the Arabidopsis cytosolic proteome highlights su... | REMOVE | Summary: NOT located in cytosol, from analysis of the Arabidopsis cytosolic proteome. Reason: The negative claim is contradicted by later direct evidence: CAT2 interacts with NCA1 in the cytosol (BiFC in protoplasts) and UniProt records cytosol as an experimental location from PMID:25700484. Absence from a cell-suspension cytosolic fraction does not establish absence from the cytosol. Supporting Evidence: PMID:25700484 NCA1 colocalizes and interacts with CAT2 in cytosol file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. |
| GO:0005886 plasma membrane | HDA PMID:28887381 Global Analysis of Membrane-associated Protein Oligomerizati... | MARK AS OVER ANNOTATED | Summary: Detected in a membrane-associated protein oligomerization proteomics survey. Reason: CAT2 is a soluble peroxisomal matrix enzyme (GFP localization, PMID:25700484) and one of the most abundant leaf peroxisomal proteins. Detection in a bulk organelle or fraction proteome of this kind is most simply explained by carry-over of peroxisomes or released matrix protein, and no targeted study shows a functional CAT2 pool in this compartment. The detection is not contradicted, but it does not describe where CAT2 acts. Action follows the ARATH convention for single high-throughput proteomics location hits (projects/ARATH/organelle-audit.md, rule 3). CAT2 has no transmembrane segment or lipid anchor. Supporting Evidence: PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 |
| GO:0005886 plasma membrane | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: Phylogenetic inference of plasma membrane activity, from a plant catalase node seeded with rice catalases. Reason: The node (PTN000157342) is supported by three rice catalases (Q0D9C4, Q0E4K1, Q10S82). Plant catalases are soluble heme enzymes acting in the peroxisomal matrix and cytosol; for CAT2 the experimental locations are peroxisome and cytosol (PMID:25700484), and the only plasma membrane evidence is a high-throughput membrane proteome. A peripheral association cannot be excluded, but the plasma membrane is not where CAT2 acts. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: COMPARTMENT OR COMPLEX MISMATCH SOURCE EVIDENCE WEAK Sources checked: PANTHER:PTN000157342 · PTN000157342 SOURCE WEAK OR INFERRED Plant catalase node whose plasma membrane assertion rests on rice catalases; plant catalases act as soluble peroxisomal and cytosolic enzymes, so a membrane location is at most a peripheral association. UniProtKB:Q0D9C4 UNRESOLVED Rice catalase donor; the experimental basis of its plasma membrane annotation was not inspected here. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Cytoplasm, cytosol {ECO:0000269|PubMed:25700484}. Peroxisome matrix {ECO:0000269|PubMed:25700484}. PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 |
| GO:0006979 response to oxidative stress | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro catalase mapping to response to oxidative stress. Reason: Catalase-deficient cat2 plants show intracellular redox perturbation and oxidative signalling in photorespiratory conditions, so CAT2 does act in responses to oxidative stress. The more mechanistic process is hydrogen peroxide catabolic process (accepted), which is not a descendant of this term, so this is kept as non-core rather than modified. Supporting Evidence: PMID:17877712 Growth of Arabidopsis knock-out mutants for CATALASE2 (cat2) in ambient air caused severely decreased rosette biomass, intracellular redox perturbation and activation of oxidative signalling pathways. PMID:15200641 Because catalases are the major H(2)O(2) scavengers that remove the bulk of cellular H(2)O(2), altering their levels allows in planta modulation of H(2)O(2) concentrations. |
| GO:0006979 response to oxidative stress | IMP PMID:17877712 Conditional oxidative stress responses in the Arabidopsis ph... | KEEP AS NON CORE | Summary: cat2 knockouts grown in air show redox perturbation and activation of oxidative signalling pathways, abolished at high CO2. Reason: Supported by the mutant phenotype; peripheral to the enzymatic core (H2O2 disproportionation). Supporting Evidence: PMID:17877712 Growth of Arabidopsis knock-out mutants for CATALASE2 (cat2) in ambient air caused severely decreased rosette biomass, intracellular redox perturbation and activation of oxidative signalling pathways. PMID:17877712 These effects were absent when cat2 was grown at high CO(2) levels to inhibit photorespiration |
| GO:0006995 cellular response to nitrogen starvation | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA machine-learning annotation to cellular response to nitrogen starvation. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. The ARBA rule adds no independent evidence. Supporting Evidence: PMID:15032878 a severe drop in CAT and APX activities, although cat1 mRNA levels were increased in young and old leaves. |
| GO:0006995 cellular response to nitrogen starvation | IEP PMID:15032878 The antioxidant status of photosynthesizing leaves under nut... | MARK AS OVER ANNOTATED | Summary: Leaf catalase activity and antioxidant transcripts change under nitrogen deprivation. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. Moreover, for nitrogen deprivation the abstract reports a drop in total CAT activity and an increase in cat1 (not cat2) mRNA (abstract-only cache; the curator may have used CAT2-specific data from the full text). Supporting Evidence: PMID:15032878 a severe drop in CAT and APX activities, although cat1 mRNA levels were increased in young and old leaves. |
| GO:0009409 response to cold | IEP PMID:16923014 The chloroplast lumen and stromal proteomes of Arabidopsis t... | MARK AS OVER ANNOTATED | Summary: Changed abundance in a DIGE proteome of chloroplast stroma and lumen during cold acclimation. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. The cited study is a chloroplast proteome in which catalase is likely a peroxisomal carry-over (abstract-only cache). Supporting Evidence: PMID:16923014 We identify 43 differentially displayed proteins that participate in photosynthesis, other plastid metabolic functions, hormone biosynthesis and stress sensing and signal transduction. |
| GO:0009409 response to cold | IEP PMID:18230142 Light has a specific role in modulating Arabidopsis gene exp... | MARK AS OVER ANNOTATED | Summary: CAT2 transcripts increased after cold treatment in the light or dark and after dark treatment. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. CAT2 was induced under Cold/Light, Cold/Dark and Dark alike, so the induction is not specific to cold. Supporting Evidence: PMID:18230142 with catalase 2 (CAT2, At4g35090) as an exception, which was clearly up regulated after all three treatments i.e. under the Cold/Light, Cold/Dark and Dark conditions. |
| GO:0009416 response to light stimulus | IEP PMID:18230142 Light has a specific role in modulating Arabidopsis gene exp... | MARK AS OVER ANNOTATED | Summary: CAT2 expression changes in a light/temperature transcript study. Reason: In the cited study CAT2 was up-regulated under Cold/Light, Cold/Dark and Dark conditions, so it does not show a specific response to light. CAT2 expression is independently described as light-stimulated and clock-regulated (PMID:22303256), but an expression response is peripheral and does not show CAT2 participates in a light response process. Supporting Evidence: PMID:18230142 with catalase 2 (CAT2, At4g35090) as an exception, which was clearly up regulated after all three treatments i.e. under the Cold/Light, Cold/Dark and Dark conditions. PMID:22303256 Cat 2 gene expression is light-stimulated and clock-regulated with an induction in the early morning |
| GO:0009648 photoperiodism | IMP PMID:17877712 Conditional oxidative stress responses in the Arabidopsis ph... | MARK AS OVER ANNOTATED | Summary: Day length determines whether cat2 mutants develop lesions in air. Reason: The photoperiod-dependence of cell death in cat2 is a conditional phenotype of excess photorespiratory H2O2; it shows that photoperiod modulates the oxidative stress outcome, not that CAT2 functions in photoperiodism (measuring day length to control development). Supporting Evidence: PMID:17877712 Growth of cat2 in air at different daylengths revealed that photoperiod is a critical determinant of the oxidative stress response. |
| GO:0009970 cellular response to sulfate starvation | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA machine-learning annotation to cellular response to sulfate starvation. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. The ARBA rule adds no independent evidence. Supporting Evidence: PMID:15032878 Transcripts of many antioxidant enzymes were unaltered or decreased, only cat2 mRNA was increased. |
| GO:0009970 cellular response to sulfate starvation | IEP PMID:15032878 The antioxidant status of photosynthesizing leaves under nut... | MARK AS OVER ANNOTATED | Summary: Under sulfur depletion only cat2 mRNA among antioxidant transcripts increased. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. Supporting Evidence: PMID:15032878 Transcripts of many antioxidant enzymes were unaltered or decreased, only cat2 mRNA was increased. |
| GO:0010319 stromule | IDA PMID:16923014 The chloroplast lumen and stromal proteomes of Arabidopsis t... | UNDECIDED | Summary: Annotation to stromule from a chloroplast stroma/lumen proteome during cold acclimation. Reason: Cached text is abstract-only and the abstract reports stroma and lumen proteomes, not stromules, so the data behind a stromule IDA call cannot be seen; per projects/ARATH/organelle-audit.md (rule 4) such an experimental row is UNDECIDED. Biologically, CAT2 has no plastid transit peptide and acts in the peroxisomal matrix (PMID:25700484), and peroxisomes are closely associated with chloroplasts, so catalase in stromal preparations would most likely reflect carry-over. Supporting Evidence: PMID:25700484 The GFP signal was predominately observed in the peroxisomes in both Col-0 and nca1-3 |
| GO:0016036 cellular response to phosphate starvation | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA machine-learning annotation to cellular response to phosphate starvation. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. The ARBA rule adds no independent evidence. Supporting Evidence: PMID:15032878 transcripts of all cat genes and stromal apx, as well as prxIIC, prxIID, were elevated under P deprivation. |
| GO:0016036 cellular response to phosphate starvation | IEP PMID:15032878 The antioxidant status of photosynthesizing leaves under nut... | MARK AS OVER ANNOTATED | Summary: Transcripts of all catalase genes and CAT activity increased under phosphate deprivation. Reason: Changes in transcript or activity levels under a condition show that CAT2 expression responds to it, not that CAT2 is part of the response process. CAT2 is an H2O2-scavenging enzyme whose expression is modulated by many stresses; the annotation is a peripheral expression observation rather than a function. Supporting Evidence: PMID:15032878 transcripts of all cat genes and stromal apx, as well as prxIIC, prxIID, were elevated under P deprivation. |
| GO:0020037 heme binding | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of heme binding. Reason: Monofunctional catalases are heme enzymes; the axial iron ligand (Tyr) is conserved (UniProt, by similarity to P04040). Heme binding is intrinsic to catalase activity. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Name=heme; Xref=ChEBI:CHEBI:30413; file:ARATH/CAT2/CAT2-uniprot.txt Belongs to the catalase family. |
| GO:0020037 heme binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro catalase mapping to heme binding. Reason: As for the IBA row: heme is the catalase cofactor. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Belongs to the catalase family. |
| GO:0022626 cytosolic ribosome | HDA PMID:15821981 High heterogeneity within the ribosomal proteins of the Arab... | MARK AS OVER ANNOTATED | Summary: Co-purified with cytosolic 80S ribosomes in a ribosome proteomics study. Reason: CAT2 is a soluble peroxisomal matrix enzyme (GFP localization, PMID:25700484) and one of the most abundant leaf peroxisomal proteins. Detection in a bulk organelle or fraction proteome of this kind is most simply explained by carry-over of peroxisomes or released matrix protein, and no targeted study shows a functional CAT2 pool in this compartment. The detection is not contradicted, but it does not describe where CAT2 acts. Action follows the ARATH convention for single high-throughput proteomics location hits (projects/ARATH/organelle-audit.md, rule 3). The study itself lists non-ribosomal proteins co-migrating with 80S ribosomes; CAT2 is not a ribosomal component. Supporting Evidence: PMID:15821981 we have identified a number of non-ribosomal proteins that co-migrate with the plant 80S ribosomes during gradient centrifugation |
| GO:0042542 response to hydrogen peroxide | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Phylogenetic inference of response to hydrogen peroxide. Reason: Catalase removes H2O2 and cat2 deficiency sensitizes plants to H2O2-induced cell death (PMID:15200641), so the term is true; the more mechanistic description of CAT2's role is hydrogen peroxide catabolic process (accepted). Non-core. Supporting Evidence: PMID:15200641 Reduced peroxisomal catalase activity increased sensitivity toward both ozone and photorespiratory H(2)O(2)-induced cell death in transgenic catalase-deficient Arabidopsis thaliana. PMID:17877712 Photorespiration is a light-dependent source of H(2)O(2) in the peroxisomes, where concentrations of this signalling molecule are regulated by catalase. |
| GO:0042744 hydrogen peroxide catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of hydrogen peroxide catabolic process. Reason: Core process: CAT2 is the main enzyme that decomposes H2O2 in leaves (about 80% of catalase activity) and specifically the photorespiratory H2O2 formed by glycolate oxidase. Supporting Evidence: PMID:25700484 deletion of CAT2 reduces catalase activity by 80% PMID:22303256 H 2 O 2 produced by the glycolate oxidase reaction is disproportionated to H 2 O and O 2 by catalase (CAT, EC 1.11.1.6) in order to prevent accumulation of reactive oxygen species. PMID:17877712 Photorespiration is a light-dependent source of H(2)O(2) in the peroxisomes, where concentrations of this signalling molecule are regulated by catalase. |
| GO:0045454 cell redox homeostasis | IMP PMID:17877712 Conditional oxidative stress responses in the Arabidopsis ph... | KEEP AS NON CORE | Summary: cat2 knockouts show intracellular redox perturbation (glutathione status) in air. Reason: Loss of CAT2 perturbs cellular redox state through accumulation of photorespiratory H2O2, so CAT2 contributes to redox homeostasis indirectly, by removing H2O2. Peripheral to its core activity. Supporting Evidence: PMID:17877712 Growth of Arabidopsis knock-out mutants for CATALASE2 (cat2) in ambient air caused severely decreased rosette biomass, intracellular redox perturbation and activation of oxidative signalling pathways. |
| GO:0050897 cobalt ion binding | HDA PMID:20018591 Divalent metal ions in plant mitochondria and their role in ... | MARK AS OVER ANNOTATED | Summary: Retained on Co2+-charged immobilized metal affinity chromatography in a mitochondrial metalloproteome study. Reason: Binding to an IMAC resin charged with Co2+ is an in vitro affinity property, not a physiological cobalt-binding function; CAT2 is a heme (iron) enzyme of the peroxisomal matrix, so its presence in mitochondrial preparations is also likely carry-over. Not contradicted (abstract-only cache) but uninformative about function. Supporting Evidence: PMID:20018591 Immobilized metal affinity chromatography charged with Cu(2+), Zn(2+), and Co(2+) was used to identify over 100 mitochondrial proteins with metal-binding properties. |
| GO:0098869 cellular oxidant detoxification | IEA GO_REF:0000108 | ACCEPT | Summary: Logical inference from catalase activity to cellular oxidant detoxification. Reason: CAT2 removes H2O2 produced by peroxisomal oxidases, protecting cells from it; catalase-deficient plants are sensitive to photorespiratory H2O2-induced cell death. Supporting Evidence: file:ARATH/CAT2/CAT2-uniprot.txt Catalyzes the degradation of hydrogen peroxide (H(2)O(2)) generated by peroxisomal oxidases to water and oxygen PMID:15200641 Reduced peroxisomal catalase activity increased sensitivity toward both ozone and photorespiratory H(2)O(2)-induced cell death in transgenic catalase-deficient Arabidopsis thaliana. |
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Download this section (compressed HTML)Q: No catalase in GO carries photorespiration (GO:0009853), although CAT2 is the major photorespiratory catalase and cat2 is a high-CO2-rescuable mutant, so this review links CAT2 to the pathway only through hydrogen peroxide catabolic process and GO-CAM causal links from glycolate oxidase. Should the H2O2-removal step instead be annotated as part of photorespiration?
Q: What fraction of CAT2 resides in the cytosol at steady state, and does the NCA1-bound cytosolic pool contribute to H2O2 removal outside peroxisomes?
Experiment: Quantify CAT2 in cytosolic versus peroxisomal fractions with CAT2-specific antibodies or tagged lines, in wild type and nca1, and measure cytosolic H2O2 with a genetically encoded sensor.
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