ahpC encodes the cytoplasmic peroxiredoxin/alkyl hydroperoxide reductase C subunit of the AhpCF peroxide-detoxification system in Pseudomonas putida KT2440. It reduces hydrogen peroxide and organic hydroperoxides, contributes to cellular oxidant detoxification and oxidative-stress defense, and is under OxyR control.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004601 peroxidase activity | IEA GO_REF:0000120 | ACCEPT | Summary: AhpC reduces peroxides through its peroxiredoxin active site. Reason: Peroxiredoxin activity is peroxidase activity. The broad parent does not become wrong because the catalytic subfamily is known. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: Cytoplasmic localization is consistent with the UniProt record and with the role of AhpC as a soluble intracellular peroxide-detoxification enzyme. Reason: The available evidence supports AhpC as a soluble cytoplasmic protein. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0005829 cytosol | IEA GO_REF:0000118 | ACCEPT | Summary: AhpC is a soluble cytosolic bacterial protein. Reason: The current cytosol definition excludes organelles but includes soluble proteins and protein complexes. It applies to bacteria; the existing cytoplasm annotation does not justify replacing this correct, more specific localization. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0006979 response to oxidative stress | IEA GO_REF:0000120 | ACCEPT | Summary: AhpC directly detoxifies peroxide during oxidative stress. Reason: Direct peroxide reduction performs work in the oxidative-stress response. The more specific detoxification annotation is complementary and does not make this core protective role peripheral. Supporting Evidence: PMID:15352239 The up-regulated proteins include proteins involved in the: (i) oxidative stress response (AhpC, SodB,Tpx and Dsb) PMID:17107553 These results are consistent with the conclusion, distinct from those observed in an opportunistic pathogen Pseudomonas aeruginosa, that OxyR controlled expression of all the principal peroxide-degrading enzymes in P. putida. file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0008379 thioredoxin peroxidase activity | IEA GO_REF:0000118 | MODIFY | Summary: The historical thioredoxin-peroxidase assignment is best represented by the current peroxiredoxin activity term. Reason: QuickGO checked on 2026-09-20 marks GO:0008379 obsolete; preserve the source GOA identifier and refine its review to the active peroxiredoxin term. Independently, the existing reports support a typical AhpC/AhpF system and distinguish its immediate protein reductant from free thioredoxin. Their donor discussion does not undermine peroxide reduction, antioxidant activity or H2O2 catabolism. Proposed replacements: peroxiredoxin activity Supporting Evidence: PMID:12483614 The most abundantly produced 24-kDa soluble protein was found to be similar to AhpC, the small subunit of alkyl hydroperoxide reductase. file:PSEPK/ahpC/ahpC-deep-research-falcon.md In P. putida, the AhpC catalytic cycle is coupled to a dedicated reductase AhpF, characterized as a flavoprotein/disulfide reductase that uses NADH as the reducing equivalent to restore AhpC from its oxidized form. file:PSEPK/ahpC/ahpC-hypotheses/function-hypothesis-go-0008379/openscientist.md Verdict: Partially supported / too general - failure mode #1 (granularity / family-vs-subfamily). file:PSEPK/ahpC/ahpC-hypotheses/function-hypothesis-go-0008379/openscientist.md **The peroxidase activity is authentic and fully supported.** file:PSEPK/ahpC/ahpC-hypotheses/function-hypothesis-go-0008379/falcon.md the physiological reductant is AhpF, a dedicated NADH:peroxiredoxin oxidoreductase co-transcribed with AhpC in an operon |
| GO:0016209 antioxidant activity | IEA GO_REF:0000002 | ACCEPT | Summary: AhpC has antioxidant activity through peroxide reduction. Reason: The broad antioxidant activity follows from the accepted peroxiredoxin reaction; it is the same core function at broader granularity. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt Plays a role in cell protection against oxidative stress by detoxifying peroxides. file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | ACCEPT | Summary: Peroxide reduction by AhpC is an oxidoreductase reaction. Reason: This broad parent is chemically entailed by peroxiredoxin activity. It is acceptable alongside the specific function. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0033554 cellular response to stress | IEA GO_REF:0000118 | ACCEPT | Summary: AhpC contributes directly to the cellular response to peroxide stress. Reason: The general stress-response annotation is supported by the direct antioxidant mechanism and OxyR-associated response. Broadness alone does not turn that response into a non-core function. Supporting Evidence: PMID:15352239 The up-regulated proteins include proteins involved in the: (i) oxidative stress response (AhpC, SodB,Tpx and Dsb) file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0042744 hydrogen peroxide catabolic process | IEA GO_REF:0000118 | ACCEPT | Summary: AhpC directly reduces and thereby destroys hydrogen peroxide. Reason: Hydrogen peroxide is among the substrates explicitly listed in the UniProt reaction/function annotation. Activity toward additional organic hydroperoxides does not invalidate the specific H2O2 catabolic process or require generalizing it. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0045454 cell redox homeostasis | IEA GO_REF:0000118 | ACCEPT | Summary: AhpC helps maintain cellular redox conditions by detoxifying peroxides. Reason: Peroxide reduction directly limits oxidative burden as part of the antioxidant system. This is a supported broad process, not merely an unrelated phenotype. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt Plays a role in cell protection against oxidative stress by detoxifying peroxides. file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0051920 peroxiredoxin activity | IEA GO_REF:0000120 | ACCEPT | Summary: This is the best existing GO molecular-function term for AhpC. The UniProt record, domain architecture, and the primary literature all support AhpC as an AhpC/Prx1-family peroxide-reducing peroxiredoxin. Reason: This term captures the core catalytic identity of the protein without overcommitting to donor-specific chemistry at the single-gene-product level. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt Belongs to the peroxiredoxin family. AhpC/Prx1 subfamily. PMID:12483614 The most abundantly produced 24-kDa soluble protein was found to be similar to AhpC, the small subunit of alkyl hydroperoxide reductase. file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0098869 cellular oxidant detoxification | IEA GO_REF:0000120 | ACCEPT | Summary: This term best captures the direct biological-process role of AhpC in peroxide removal. The enzyme detoxifies peroxides and is part of the OxyR-controlled peroxide-defense system in P. putida. Reason: The process term aligns with both the known chemistry of the enzyme and the regulatory/physiological evidence from P. putida. Supporting Evidence: file:PSEPK/ahpC/ahpC-uniprot.txt Plays a role in cell protection against oxidative stress by detoxifying peroxides. PMID:17107553 These results are consistent with the conclusion, distinct from those observed in an opportunistic pathogen Pseudomonas aeruginosa, that OxyR controlled expression of all the principal peroxide-degrading enzymes in P. putida. file:PSEPK/ahpC/ahpC-uniprot.txt Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. |
| GO:0102039 NADH-dependent peroxiredoxin activity | IEA GO_REF:0000120 | MODIFY | Summary: This term likely reflects the chemistry of the AhpCF system rather than the AhpC subunit alone. AhpC is the peroxiredoxin component, whereas AhpF provides the NADH-linked reductant flow. Reason: The coupled AhpCF system is NADH-dependent, as recognized by both existing reports. AhpC directly reduces peroxide while AhpF supplies electrons from NADH. Retain the donor-independent single-subunit refinement to peroxiredoxin activity; this is a gene-product scope distinction, not a claim that NADH-dependent AhpCF physiology is absent. Whether GO:0102039 is conventionally assigned to the catalytic AhpC subunit itself remains a useful curation second opinion. Proposed replacements: peroxiredoxin activity Supporting Evidence: PMID:12483614 Molecular cloning of the P. putida ahpC based on the N-terminal sequence allowed cloning of closely located ahpF, the large subunit of alkyl hydroperoxide reductase. file:PSEPK/ahpC/ahpC-deep-research-falcon.md In P. putida, the AhpC catalytic cycle is coupled to a dedicated reductase AhpF, characterized as a flavoprotein/disulfide reductase that uses NADH as the reducing equivalent to restore AhpC from its oxidized form. |
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Download this section (compressed HTML)Q: What is the in vivo substrate preference of P. putida AhpC for hydrogen peroxide versus organic hydroperoxides under different stress conditions?
Q: Does P. putida AhpC function exclusively with AhpF in vivo, or can it also draw reducing equivalents from thioredoxin-dependent systems?
Experiment: Purify P. putida AhpC together with AhpF and measure steady-state kinetics against hydrogen peroxide and several organic hydroperoxides to resolve substrate preference and donor coupling.
Hypothesis: P. putida AhpC will show higher catalytic efficiency toward organic hydroperoxides than toward hydrogen peroxide under AhpF/NADH-coupled assay conditions.
Type: Enzyme kinetics with purified proteins
Experiment: Construct an ahpC deletion mutant and quantify growth, survival, and oxidant sensitivity during exposure to hydrogen peroxide, tert-butyl hydroperoxide, phenol, and toluene, followed by complementation with wild-type ahpC.
Hypothesis: Loss of ahpC will disproportionately sensitize P. putida to organic hydroperoxides and solvent-associated oxidative stress.
Type: Targeted knockout and stress-phenotyping assay
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