| Aspect | Evidence/Findings (concise) | Organism/Strain | Quantitative data (if any) | Primary source (author year journal) | DOI/URL |
|---|---|---|---|---|---|
| Identity | gltA is explicitly identified as the gene encoding citrate synthase in *Pseudomonas putida*; in KT2440 studies it was the target for overexpression or deletion as a central-carbon enzyme (pqac-00000009, pqac-00000010, pqac-00000014) | *P. putida* KT2440; derived strains gltA-KT, QSRZ602/QSRZ603/QSRZ606/QSRZ607 | — | Mutyala et al. 2023, *ACS Omega*; Dong et al. 2024, *Current Issues in Molecular Biology* | https://doi.org/10.1021/acsomega.3c02520 ; https://doi.org/10.3390/cimb46110761 |
| Reaction | In pathway context, citrate synthase GltA initiates acetate metabolism by converting acetyl-CoA to citrate; related *Pseudomonas* biochemical work assayed GltA with acetyl-CoA + oxaloacetate and found no detectable 2-methylcitrate synthase activity (pqac-00000017, pqac-00000019) | *P. putida* KT2440; *P. aeruginosa* GltA (comparative evidence) | Substrates/products stated: acetyl-CoA → citrate in KT2440 pathway context; acetyl-CoA + OAA assayed in *P. aeruginosa* | Mutyala et al. 2023, *ACS Omega*; Dolan et al. 2022, *mBio* | https://doi.org/10.1021/acsomega.3c02520 ; https://doi.org/10.1128/mbio.02541-22 |
| Pathway role | GltA sits at the entry of acetyl-CoA into the TCA cycle and is described as a bottleneck for acetate assimilation into the TCA cycle; deleting gltA is used to prevent acetyl-CoA from entering the TCA cycle and increase malonyl-CoA availability (pqac-00000025, pqac-00000023) | *P. putida* KT2440 / SEM11-derived engineering strains | gltA overexpression alone gave 9.5% of maximum theoretical succinate yield from acetate (pqac-00000025) | Mutyala et al. 2023, *ACS Omega*; Favoino et al. 2024, *Microbial Biotechnology* | https://doi.org/10.1021/acsomega.3c02520 ; https://doi.org/10.1111/1751-7915.70044 |
| Localization | No explicit subcellular localization for KT2440 GltA was reported in the gathered evidence; available studies discuss it as a central metabolic enzyme without localization data (pqac-00000017, pqac-00000018, pqac-00000022) | *P. putida* KT2440 | — | Mutyala et al. 2023, *ACS Omega*; Dong et al. 2024, *Current Issues in Molecular Biology* | https://doi.org/10.1021/acsomega.3c02520 ; https://doi.org/10.3390/cimb46110761 |
| Essentiality | A KT2440 conditional-essentiality study used gltA as a highly expressed internal calibrator and stated that gltA expression is essential under all growth conditions for this strict aerobe; however, later engineering studies successfully constructed ΔgltA mutants that grew on glucose batch cultures, implying gltA is not absolutely essential under those tested conditions (expression-essentiality statement vs knockout viability under specific conditions) (pqac-00000028, pqac-00000022) | *P. putida* KT2440; QSRZ602/QSRZ603 derivatives | gltA relative expression benchmark: 14,500 units (pqac-00000028); ΔgltA single mutant had similar growth/glucose consumption to parent on 20 g/L glucose (pqac-00000022) | Molina-Henares et al. 2010, *Environmental Microbiology*; Dong et al. 2024, *Current Issues in Molecular Biology* | https://doi.org/10.1111/j.1462-2920.2010.02166.x ; https://doi.org/10.3390/cimb46110761 |
| Engineering perturbation: overexpression for succinate | IPTG-inducible gltA overexpression (gltA-KT) increased succinate production from acetate under microaerobic conditions; pH control improved output further (pqac-00000020, pqac-00000021) | *P. putida* KT2440 gltA-KT | 4.73 ± 0.63 mM succinate at pH 7.5 vs WT 0.99 ± 0.13 mM (~4.7×); 3.35 ± 0.27 mM at pH 8.0; 2.64 ± 0.11 mM from 100 mM acetate without pH control; ~50% higher succinate from acetate than glucose (4.73 ± 0.63 vs 2.3 ± 0.05 mM); resting cells 4.94 ± 0.04 mM; WT microaerobic baseline 1.24 ± 0.17 mM from 100 mM acetate (pqac-00000020, pqac-00000021, pqac-00000026) | Mutyala et al. 2023, *ACS Omega* | https://doi.org/10.1021/acsomega.3c02520 |
| Engineering perturbation: deletion for mcl-PHA | Deleting gltA redirected carbon from the TCA cycle to mcl-PHA synthesis; single and combinatorial mutants improved polymer accumulation (pqac-00000022) | *P. putida* QSRZ6 derivatives | ΔgltA (QSRZ602): 32.6 wt% mcl-PHA and 1.2 g/L vs parent 27.3 wt% and 1.0 g/L; ΔgcdΔgltA (QSRZ603): 37.6 wt%, 1.3 g/L; ΔhexRΔgltA (QSRZ606): 39.5 wt%, 1.4 g/L; ΔhexRΔgcdΔgltA (QSRZ607): 49.1 wt%, 2.1 g/L (pqac-00000022) | Dong et al. 2024, *Current Issues in Molecular Biology* | https://doi.org/10.3390/cimb46110761 |
| Engineering perturbation: deletion/CRISPRi for malonyl-CoA/PHB | gltA deletion or repression was used as a design strategy to prevent acetyl-CoA entry into the TCA cycle and increase malonyl-CoA availability for PHB/PHA pathways; pages retrieved reported qualitative benefit but not a gltA-specific numeric titer (pqac-00000023) | *P. putida* SEM11-derived engineered strains | Qualitative: increased malonyl-CoA/biopolymer accumulation, but reduced μmax and longer lag phases; no gltA-specific numeric titer in retrieved pages (pqac-00000023) | Favoino et al. 2024, *Microbial Biotechnology* | https://doi.org/10.1111/1751-7915.70044 |
| Comparative structural/biochemical evidence | In related *Pseudomonas*, GltA is a type II-like bacterial citrate synthase with canonical catalytic triad and likely NADH regulation; forms a hexameric trimer of dimers and lacks detectable 2-methylcitrate synthase activity (useful for family-level inference, not direct KT2440 proof) (pqac-00000019) | *P. aeruginosa* GltA (comparative family evidence) | 429 aa; hexameric trimer of dimers; catalytic triad His-265/His-306/Asp-363 (pqac-00000019) | Dolan et al. 2022, *mBio* | https://doi.org/10.1128/mbio.02541-22 |
| Broader physiological significance outside KT2440 | In *Pseudomonas fluorescens* 2P24, gltA mutation reduced 2,4-DAPG biosynthesis and biocontrol capacity, supporting a broader role for citrate synthase-derived citrate in regulatory physiology across pseudomonads (comparative evidence) (pqac-00000013) | *P. fluorescens* 2P24 | 946 DEGs; disease index 84.9% in gltA mutant vs 45.7% WT; plant survival 15.1% vs 54.3% WT (pqac-00000013) | Yang et al. 2023, *Journal of Agricultural and Food Chemistry* | https://doi.org/10.1021/acs.jafc.3c03051 |


*Table: This table summarizes core functional annotation facts for *Pseudomonas putida* KT2440 gltA/Q88FA4 using only the gathered evidence. It highlights identity, catalytic role, pathway placement, unresolved localization, nuanced essentiality evidence, and quantitative outcomes from recent metabolic engineering studies.*