| Aspect | Key points | Best supporting sources |
|---|---|---|
| Identity | Target is **acnB / PP_2339** in *Pseudomonas putida* KT2440; KT2440-focused studies annotate it as a **bifunctional 2-methylcitrate dehydratase/aconitase hydratase B**, matching UniProt Q88KF1. | (pqac-00000000, pqac-00000001, pqac-00000002) |
| Enzymatic activities | Evidence supports dual activity as **aconitate hydratase (aconitase)** in central metabolism and **2-methylcitrate/2-methylisocitrate dehydratase-related activity** in the methylcitrate cycle; literature places AcnB at the rehydration/dehydration steps around methylaconitate/2-methylisocitrate. | (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000011) |
| Pathway roles | AcnB links the **TCA cycle** and the **methylcitrate cycle (MCC)** used for assimilation/detoxification of propionyl-CoA derived from **odd-chain fatty acids**; MCC yields **succinate and pyruvate** for central metabolism. | (pqac-00000000, pqac-00000001, pqac-00000003, pqac-00000011) |
| Cofactor & sensitivity | As an aconitase-family enzyme, AcnB is expected to use a **[4Fe-4S] cluster**; broader aconitase literature indicates this cofactor is required for catalysis and is **sensitive to oxidation/iron limitation**, with AcnB often less stable than AcnA under oxidative stress. This is strong family-level inference, not direct KT2440 biochemical proof. | (pqac-00000004, pqac-00000006, pqac-00000009) |
| Regulation / moonlighting | Direct **KT2440-specific moonlighting/RNA-binding evidence was not found**. In other bacteria, apo-AcnB can become an **RNA-binding post-transcriptional regulator** after Fe-S cluster loss, so this is a plausible family property but currently **unproven for PP_2339 in KT2440**. Proteomics in KT2440 shows AcnB abundance remains relatively stable from early to mid exponential growth. | (pqac-00000003, pqac-00000004, pqac-00000006) |
| Phenotypes / essentiality | **No mapped transposon insertions** were recovered for PP_2339 in RB-TnSeq studies, interpreted by the authors as suggesting **essentiality during library construction**. Neighboring MCC genes show strong odd-chain-fatty-acid fitness phenotypes, and authors infer PP_2339 likely provides much of the methylaconitate hydratase activity in this pathway. | (pqac-00000000, pqac-00000002, pqac-00000011) |
| Localization | No direct localization experiment for PP_2339 was identified in the retrieved evidence. Based on its roles in the **TCA/MCC soluble metabolic network** and the aconitase enzyme class, AcnB is **best inferred to be a cytosolic enzyme** rather than membrane or extracellular. | (pqac-00000000, pqac-00000003) |


*Table: This table summarizes the currently supported functional annotation for *Pseudomonas putida* KT2440 acnB (PP_2339; UniProt Q88KF1). It distinguishes direct KT2440 evidence from broader aconitase-family inference, which is useful where organism-specific biochemical data are limited.*