Type II (1-Cys, glutaredoxin/thioredoxin-dependent) peroxiredoxin of the Prx5 subfamily. It is a thiol-based peroxidase that uses a conserved redox-active peroxidatic cysteine to reduce hydrogen peroxide and organic, fatty acid, and phospholipid hydroperoxides to water and the corresponding alcohols, receiving reducing equivalents preferentially from glutaredoxin or from thioredoxin. Through peroxide detoxification it contributes to cell protection against oxidative stress and to cellular redox homeostasis.
The preferred accession for this review is A9PCL4. These relationships are manually assessed.
REFERENCE PROTEOME EQUIVALENT · Reviewed 2026-10-19
Reference proteome: UP000006729
Retain A9PCL4 as the primary Swiss-Prot accession. B9ILP9 at POPTR_018G083500 is the manually assessed reference-proteome counterpart: 161/162 identical residues, full ungapped coverage, and only N117D. The competing POPTR_001G423500 paralog (A0A2K2CCD0) differs at seven residues. The original EF146010 cDNA is explicitly from Nisqually-1, so a different cultivar cannot explain this pair. This is a sequence-supported locus assignment, not a shared primary-record locus cross-reference; the one-residue discrepancy remains unexplained.
MMseqs2 searched all 77,340 sequences in UP000006729 (release 2026_03); global BLOSUM62 alignments were computed for every returned hit. B9ILP9 ranks first by global alignment score, with 99.3827% identity including gap columns, 100.0% query coverage and 100.0% target coverage. The saved candidate table and alignments retain competing matches and residue-level differences. The search is heuristic, and sequence similarity alone is not definitive genomic mapping. Identity over paired residues is 99.3827% (161/162); gap columns are excluded from this denominator.
file:POPTR/PRX2/PRX2-record-evidence.yaml
query_length: 162 target_length: 162 alignment_columns: 162 identities: 161 mismatches: 1 gap_columns: 0 identity_percent: 99.3827 query_coverage_percent: 100.0 target_coverage_percent: 100.0
Current UniProtKB and proteome records place B9ILP9, but not A9PCL4, in reference proteome UP000006729. Both UniProt records use NCBITaxon:3694; source-organism qualifications are recorded separately.
file:POPTR/PRX2/PRX2-record-evidence.yaml
reference_proteome: UP000006729 proteome_is_reference: true proteome_taxon_matches: true primary_in_reference_proteome: false alternative_in_reference_proteome: true
UniSave versions 37 (2015), 62 (2020), and 77 (2024) lack Proteomes cross-references. These dated samples support longstanding absence at those dates; they do not establish uninterrupted absence, a removal event, or UniProt's motivation.
file:POPTR/PRX2/PRX2-record-evidence.yaml
sampled_history_versions: - 37 - 62 - 77 sampled_versions_with_proteome_links: []
ENA source EF146010 identifies cultivar 383-2499 (Nisqually-1), matching the reference cultivar. The sequence discrepancy could reflect allele or sequence/model differences; the records do not establish which explanation applies.
file:POPTR/PRX2/PRX2-record-evidence.yaml
/cultivar="383-2499 (Nisqually-1)"
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0008379 thioredoxin peroxidase activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Thioredoxin peroxidase activity is supported because the enzyme can use thioredoxin as a reductant, but the protein preferentially uses glutaredoxin, so this term captures only part of the demonstrated activity. Reason: UniProt and the biochemical literature show this peroxiredoxin uses either glutaredoxin or thioredoxin as a proton donor and preferentially uses glutaredoxin; the more general peroxiredoxin activity term better represents the core function, while thioredoxin peroxidase activity remains a correct supporting molecular function. Supporting Evidence: file:POPTR/PRX2/PRX2-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols file:POPTR/PRX2/PRX2-deep-research-openai.md Peroxiredoxin activity reducing peroxides with electron donation via thioredoxin and/or glutaredoxin systems. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Oxidoreductase activity is correct but is a high-level parent term that is less informative than the specific peroxiredoxin activity for this characterized enzyme. Reason: The specific peroxiredoxin activity and thioredoxin peroxidase activity terms already capture the redox catalysis; the generic oxidoreductase parent is true but redundant, so it is retained as a non-core annotation rather than the principal function. Supporting Evidence: file:POPTR/PRX2/PRX2-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols |
| GO:0034599 cellular response to oxidative stress | IEA GO_REF:0000002 | ACCEPT | Summary: Cellular response to oxidative stress is the direct biological process for this peroxide-detoxifying antioxidant enzyme. Reason: UniProt states the protein plays a role in cell protection against oxidative stress by detoxifying peroxides, which is exactly a cellular response to oxidative stress. Supporting Evidence: file:POPTR/PRX2/PRX2-uniprot.txt Plays a role in cell protection against oxidative stress by detoxifying peroxides. file:POPTR/PRX2/PRX2-deep-research-openai.md Redox buffering and peroxide detoxification functions are consistent with stress-responsive antioxidant networks in plant tissues. |
| GO:0051920 peroxiredoxin activity | IEA GO_REF:0000116 | ACCEPT | Summary: Peroxiredoxin activity is the precise core molecular function, matching the glutaredoxin-dependent hydroperoxide reduction reaction and EC 1.11.1.25. Reason: UniProt records the glutaredoxin-dependent reduction of hydroperoxides under EC 1.11.1.25, which is exactly peroxiredoxin activity, and the enzyme belongs to the peroxiredoxin family. Supporting Evidence: file:POPTR/PRX2/PRX2-uniprot.txt Reaction=[glutaredoxin]-dithiol + a hydroperoxide = [glutaredoxin]- file:POPTR/PRX2/PRX2-deep-research-openai.md Peroxiredoxin activity reducing peroxides with electron donation via thioredoxin and/or glutaredoxin systems. |
| GO:0098869 cellular oxidant detoxification | IEA GO_REF:0000120 | ACCEPT | Summary: Cellular oxidant detoxification fits the role of this peroxiredoxin in detoxifying peroxides to protect the cell. Reason: The enzyme detoxifies hydrogen peroxide and organic hydroperoxides, which is a cellular oxidant detoxification process underlying its protective antioxidant role. Supporting Evidence: file:POPTR/PRX2/PRX2-uniprot.txt Plays a role in cell protection against oxidative stress by detoxifying peroxides. file:POPTR/PRX2/PRX2-deep-research-openai.md Redox buffering and peroxide detoxification functions are consistent with stress-responsive antioxidant networks in plant tissues. |
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Experiment: Assay recombinant PRX2 peroxidase activity against hydrogen peroxide and phospholipid hydroperoxides with glutaredoxin versus thioredoxin reducing systems, and characterize the catalytic cysteine via site-directed mutagenesis.
Type: targeted enzymatic and mechanistic assay
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