KatA (PA4236) is the major catalase of Pseudomonas aeruginosa, a heme-containing monofunctional (clade 3) catalase that dismutates hydrogen peroxide into water and oxygen (EC 1.11.1.6). It is a homotetramer with one heme per subunit and a bound NADPH, and it is an abundant, protease-resistant cytoplasmic protein. katA mutants have no detectable catalase activity and are hypersusceptible to H2O2, and katA transcription rises with iron and H2O2. Full KatA activity needs the iron-storage protein bacterioferritin A, a likely iron source for its heme. KatA is also more highly expressed under anaerobic growth, partly under ANR control and dependent on basal nitric oxide. Its ferric heme binds NO directly (Kd about 6 microM) without prior reduction, and katA mutants are more sensitive to nitrite-derived NO in anaerobic planktonic and biofilm cultures, suggesting that KatA also buffers NO generated during anaerobic respiration.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004096 catalase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000157250 (clade 3 monofunctional catalases, 25 seeds including human CAT P04040, MGI:88271, RGD:2279, yeast CTA1 and CTT1, Arabidopsis AT4G35090, Drosophila Cat, two C. elegans genes, and KatA itself). KatA in WITH/FROM is its expected self-seed. Reason: Core activity with direct biochemical support; the IBD is heavily seeded. Supporting Evidence: PMID:10368148 apparent Km for H2O2 of 44.7 mM file:PSEAE/katA/katA-uniprot.txt PF00199; Catalase |
| GO:0004096 catalase activity | IDA PMID:10368148 Bacterioferritin A modulates catalase A (KatA) activity and ... | ACCEPT | Summary: PseudoCAP IDA and one of 25 seeds of the PTN000157250 IBD. Ma et al. purified KatA to homogeneity (from a katB mutant of strain FRD2, and as a His-tagged recombinant protein), measured an apparent Km for H2O2 of 44.7 mM, showed that katA complements a catalase-deficient E. coli strain, and showed that katA mutants lack catalase activity. Reason: Seed is SOUND: purified-enzyme kinetics plus complementation and loss of activity in the mutant. Supporting Evidence: PMID:10368148 KatA was purified to homogeneity from a katB mutant of P. aeruginosa FRD2 PMID:10368148 apparent Km for H2O2 of 44.7 mM PMID:10368148 the P. aeruginosa katA gene complemented a catalase-deficient strain of Escherichia coli PMID:10368148 The katA and katA bfrA mutants possessed no detectable catalase activity |
| GO:0004096 catalase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined EC/Rhea/InterPro mapping; same claim as the experimental rows. Reason: Consistent with direct evidence. Supporting Evidence: PMID:10368148 apparent Km for H2O2 of 44.7 mM |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: IBA cytoplasm (is_active_in). KatA has no signal peptide and is a soluble abundant protein; clade 3 catalases are cytosolic or peroxisomal, and bacteria have no peroxisomes. Reason: No contrary evidence; consistent with a soluble catalase lacking any targeting signal. No direct localisation study was read. Supporting Evidence: PMID:24663218 KatA is the major catalase of PA that detoxifies hydrogen peroxide (H2O2) |
| GO:0006979 response to oxidative stress | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO response to oxidative stress. True, but GO:0042542 response to hydrogen peroxide, accepted here, is_a descendant. Reason: Entailed by the accepted GO:0042542. |
| GO:0020037 heme binding | IBA GO_REF:0000033 | ACCEPT | Summary: IBA heme binding (seed human CAT). KatA carries a heme prosthetic group, observed spectroscopically and crystallographically as a high-spin ferric heme. Reason: Heme is the catalytic cofactor; directly observed for KatA. Supporting Evidence: PMID:24663218 KatA has a 5-coordinate high spin ferric heme that binds NO without prior reduction of the heme iron PMID:10368148 P. aeruginosa BfrA may be required as one source of iron for the heme prosthetic group of KatA |
| GO:0020037 heme binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO heme binding; same claim. Reason: Consistent with direct observation of KatA heme. Supporting Evidence: PMID:24663218 KatA has a 5-coordinate high spin ferric heme that binds NO without prior reduction of the heme iron |
| GO:0042542 response to hydrogen peroxide | IBA GO_REF:0000033 | ACCEPT | Summary: IBA response to hydrogen peroxide. katA mutants are hypersusceptible to H2O2, and katA transcription increases with H2O2; KatA is the effector that removes the stressor. Reason: KatA directly detoxifies the stressor; mutant and induction data agree. Supporting Evidence: PMID:10368148 Isogenic katA and bfrA mutants were hypersusceptible to H2O2 |
| GO:0042744 hydrogen peroxide catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA hydrogen peroxide catabolic process. KatA catalyses the decomposition of H2O2. Reason: Direct catalytic participation. Supporting Evidence: PMID:10368148 apparent Km for H2O2 of 44.7 mM PMID:10368148 The katA and katA bfrA mutants possessed no detectable catalase activity |
| GO:0042744 hydrogen peroxide catabolic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO hydrogen peroxide catabolic process; same claim. Reason: Consistent with the IBA and experimental evidence. Supporting Evidence: PMID:10368148 apparent Km for H2O2 of 44.7 mM |
| GO:0098869 cellular oxidant detoxification | IEA GO_REF:0000108 | ACCEPT | Summary: GO_REF:0000108 inference from catalase activity to cellular oxidant detoxification. KatA removes H2O2 and protects the cell from it. Reason: Detoxification of H2O2 is the physiological role of the catalase activity. Supporting Evidence: PMID:24663218 KatA is the major catalase of PA that detoxifies hydrogen peroxide (H2O2) PMID:10368148 Isogenic katA and bfrA mutants were hypersusceptible to H2O2 |
| GO:0070026 nitric oxide binding | IDA PMID:24663218 Catalase (KatA) plays a role in protection against anaerobic... | NEW | Summary: Purified KatA binds NO at its ferric heme, shown by EPR, optical spectroscopy and X-ray crystallography (Kd about 6 microM), without prior reduction of the heme iron. Reason: Direct binding assays and a structure on the gene product itself; the binding is proposed to buffer NO during anaerobic respiration. Non-core relative to catalase activity. Supporting Evidence: PMID:24663218 KatA has a 5-coordinate high spin ferric heme that binds NO without prior reduction of the heme iron PMID:24663218 We further revealed direct NO-KatA interactions in vitro using EPR, optical spectroscopy and X-ray crystallography |
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Experiment: Measure catalase turnover of purified KatA across a range of NO concentrations and test whether KatA lowers free NO in anaerobic norCB mutants by direct NO-electrode measurements with heme-site mutants.
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