| Residue Position in *P. putida* AhpC | Equivalent Position in *S. typhimurium* AhpC (P0A251) | Equivalent Position in *B. thailandensis* AhpC | Equivalent Position in *M. bovis* AhpC | Role/Function | Conservation Status | Note |
|---|---|---|---|---|---|---|
| Cys47 | Cys46 | Cys57 | Cys61 | Peroxidatic cysteine (CP); attacks peroxide substrate to form sulfenic acid intermediate | CONSERVED | Essential catalytic cysteine of typical 2-Cys AhpC/Prx1 enzymes; directly matches experimentally defined CP residues in characterized homologs (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000003, pqac-00000032) |
| Cys166 | Cys165 | Cys171 plus nearby Cys173 in *B. thailandensis* | Cys174 | Resolving cysteine (CR); condenses with oxidized CP to form catalytic disulfide | CONSERVED | Matches experimentally defined resolving cysteine position of active AhpC homologs; *B. thailandensis* has an extra resolving-region cysteine but retains the same AhpC catalytic logic (pqac-00000000, pqac-00000002, pqac-00000003, pqac-00000032) |
| Thr/Pro motif around Cys47 | Thr/Pro motif around Cys46 | Thr/Pro motif around Cys57 | Thr/Pro motif around Cys61 | Canonical active-site environment of Prx1/AhpC typical 2-Cys peroxiredoxins; supports CP reactivity and family placement | CONSERVED | Preserved catalytic-region architecture supports placement in the Prx1/AhpC typical 2-Cys subfamily (pqac-00000016, pqac-00000017, pqac-00000032) |
| Overall sequence relationship | 69 percent identity to *S. typhimurium* AhpC | Conserved AhpC-family architecture | Conserved AhpC-family architecture | Nearest characterized-function placement | CONSERVED FAMILY CORE | High identity to classical AhpC, plus conserved catalytic cysteines, supports assignment to active AhpC/peroxiredoxin rather than another Prx subfamily; P. putida AhpC also shows 65 percent identity to *P. aeruginosa* and 65 percent similarity to *A. xylanus* AhpC homologs (pqac-00000026, pqac-00000032) |
| Subfamily placement | AhpC / Prx1 | AhpC / Prx1 | AhpC / Prx1 | Typical 2-Cys peroxiredoxin subfamily assignment | CONSERVED | No evidence for mis-placement into Prx5, Prx6, Tpx, or other neighboring peroxiredoxin subfamilies (pqac-00000016, pqac-00000017, pqac-00000018) |
| Genomic and electron-donor context | ahpC-ahpF operon in classical AhpCF arrangement | AhpC reduced by AhpF in classical system | AhpC can use AhpD and TrxC in that species | AhpC can interact with thioredoxin-C in that species | Functional context and donor specificity | QUALIFIED | In *P. putida*, ahpC is co-transcribed with ahpF and AhpF is the dedicated reductant; this argues against the donor-specific GO term thioredoxin peroxidase activity even though the enzyme is clearly an active peroxiredoxin (pqac-00000006, pqac-00000014, pqac-00000019, pqac-00000026, pqac-00000027, pqac-00000031) |
| Conclusion | Active-site architecture intact | Active-site architecture intact | Active-site architecture intact | Final placement and catalytic competence | SUPPORTED FOR CATALYSIS | Active site fully intact, catalysis predicted, no pseudo-enzyme features. Q88K52 is an active Prx1/AhpC typical 2-Cys peroxiredoxin. The annotation issue is electron-donor specificity of GO:0008379, not active-site integrity or wrong superfamily placement (pqac-00000000, pqac-00000016, pqac-00000026, pqac-00000032, pqac-00000036) |


*Table: This table summarizes catalytic-residue conservation and subfamily placement for Pseudomonas putida AhpC relative to characterized homologs. It shows that Q88K52 is a bona fide active typical 2-Cys peroxiredoxin, with the main curation issue being donor-specific GO term specificity rather than catalytic loss.*