| Annotation aspect | Evidence summary for **aroH / PP_1866 / UniProt Q88LR3** in *Pseudomonas putida* KT2440 | Notes / citations |
|---|---|---|
| Gene/protein identity | Q88LR3 is annotated as **phospho-2-dehydro-3-deoxyheptonate aldolase** (EC 2.5.1.54), i.e. a **DAHP synthase / DAH7PS** family enzyme; ordered locus **PP_1866** and gene name **aroH** match the requested target. Literature on *P. putida* KT2440 is limited, so much mechanistic detail is inferred from class-II DAHP synthase literature and DAHP-synthase isoenzyme conventions. | Functional inference is consistent with DAHP synthase annotations and class-II family discussion; direct *P. putida* biochemical characterization was not found in retrieved evidence. (pqac-00000011, pqac-00000005) |
| Enzyme family / structural class | Best-supported assignment is **class-II / type-II DAH7PS**. Characterized type-II DAH7PS enzymes share a **(β/α)8 TIM-barrel fold**, conserved metal-binding site, and conserved PEP/E4P-binding residues. This is compatible with the UniProt/InterPro/Pfam context for Q88LR3 (**PF01474 / DAHP_synth_2**). | Type-II DAH7PS structural features were described directly for characterized enzymes; application to Q88LR3 is by family inference. (pqac-00000005, pqac-00000001) |
| Catalytic reaction / substrate specificity | DAHP synthases catalyze the **condensation of phosphoenolpyruvate (PEP) and erythrose-4-phosphate (E4P) to form DAHP/DAH7P**, the first committed step of the shikimate pathway leading to chorismate and aromatic amino acids. No alternative substrate specificity for *P. putida* AroH was found. | This reaction is directly stated for DAHP synthases and class-II examples. (pqac-00000010, pqac-00000011, pqac-00000005) |
| Pathway role in *P. putida* | AroH is inferred to function in **entry into the shikimate pathway**, supplying flux toward chorismate and downstream biosynthesis of **Trp, Phe, Tyr** and other chorismate-derived metabolites. In engineering literature, increasing DAHP synthase flux is treated as a major leverage point for aromatic production in *P. putida*. | Rate control at DAHP synthase is emphasized in shikimate-pathway engineering studies. (pqac-00000003, pqac-00000012, pqac-00000014) |
| Feedback regulation | General DAHP-synthase isoenzyme convention assigns **AroH as the Trp-sensitive isoenzyme**; the 2023 *P. putida* engineering study explicitly reiterates that **AroF, AroG, and AroH are inhibited by Tyr, Phe, and Trp, respectively**. For a class-II comparator, *Xanthomonas campestris* AroAII shows **Trp noncompetitive inhibition** and **chorismate competitive inhibition**. | *P. putida* KT2440-specific inhibition constants for AroH were not found. Comparator class-II kinetics: **Km PEP 0.13 mM; Km E4P 0.23 mM; Ki chorismate 0.31 mM vs PEP and 0.09 mM vs E4P; Ki Trp 0.35 mM vs PEP and 0.61 mM vs E4P**. (pqac-00000016, pqac-00000017, pqac-00000004, pqac-00000020) |
| Localization inference | The most likely localization for *P. putida* AroH is **cytosolic**, because canonical DAHP synthases act on soluble central-metabolism substrates (PEP, E4P) in the shikimate pathway. However, class-II exceptions exist: some bacterial AroAII enzymes, such as the *X. campestris* example, have a predicted **N-terminal membrane/periplasm-associated segment**; smaller AroAII proteins lacking that region are inferred to be soluble. | Thus, membrane association is a known class-II exception, but no evidence was found that **PP_1866/Q88LR3** has such an extension; soluble/cytosolic annotation remains the best inference. (pqac-00000010, pqac-00000009, pqac-00000004) |
| Real-world implementation in *P. putida* (2016) | In *P. putida* KT2440, boosting shikimate-pathway entry with a **feedback-resistant DAHP synthase aroG D146N** plus **ubiC**, combined with deletion of **pobA, pheA, trpE, hexR**, enabled **para-hydroxybenzoic acid (PHBA)** production. | Reported best performance: **1.73 g/L PHBA** and **18.1% C-mol/C-mol** in non-optimized fed-batch. This shows the practical importance of relieving DAHP synthase control, even though the engineered enzyme was AroG rather than native AroH. (pqac-00000012, pqac-00000013, pqac-00000014) |
| Real-world implementation in *P. putida* (2023) | A 2023 KT2440 gallic-acid study used a heterologous **feedback-resistant aroG4 (Pro150Leu)** with downstream pathway genes and deletion of **pcaHG** and **galTAPR** to redirect shikimate-derived flux. The study again states AroH is the **Trp-inhibited** DAHP synthase isoenzyme. | Final reported production: **346.7 ± 0.004 mg/L gallic acid after 72 h** in shaker culture. This further supports DAHP-synthase deregulation as a real-world strategy in *P. putida* aromatic bioproduction. (pqac-00000016, pqac-00000017, pqac-00000019) |


*Table: This table summarizes the strongest available evidence for functional annotation of *Pseudomonas putida* KT2440 aroH (Q88LR3/PP_1866), combining direct *P. putida* pathway-engineering evidence with mechanistic data from characterized class-II DAHP synthases. It is useful for separating target-specific facts from family-level inference where direct biochemical characterization is limited.*