| Evidence type | Key finding | Quantitative details | Experimental context | Source (authors, year, journal, DOI URL) | Citation ID |
|---|---|---|---|---|---|
| Annotation | In *Pseudomonas putida* KT2440, the genome encodes three fumarase isoenzymes: fumA (PP_0897), fumC1 (PP_0944), and fumC2 (PP_1755). This supports identification of UniProt Q88M20 as fumC2/PP_1755. | Three fumarase loci identified | KT2440 gene inventory and isoenzyme assignment in analysis of the ΔapaH mutant | Agulló Carvajal, 2014, thesis/dissertation, DOI URL: not available in retrieved context | (pqac-00000002) |
| Biochemistry | FumC2 (PP_1755) appears able to compensate for altered fumarase function in KT2440, consistent with assignment as a fumarase C-type isoenzyme. | FumC2 induced ~4-fold; FumA repressed ~1.3-fold; total fumarase activity similar between WT and ΔapaH; FumC-specific activity significantly higher in ΔapaH | Proteomic and enzymatic analysis of *P. putida* KT2440 ΔapaH | Agulló Carvajal, 2014, thesis/dissertation, DOI URL: not available in retrieved context | (pqac-00000024) |
| Stress response | A fumC homolog in KT2440 (fumC-1) is induced by superoxide and nitric oxide stress, supporting the broader role of fumarase C isoenzymes in oxidative stress adaptation in *P. putida*. | Qualitative induction reported; no fold-change given in extracted text | Oxidative stress response review summarizing KT2440 gene induction data | Kim and Park, 2014, *Applied Microbiology and Biotechnology*, https://doi.org/10.1007/s00253-014-5883-4 | (pqac-00000011) |
| Stress response | Fumarase C abundance decreases under DCC herbicide-metabolite stress in KT2440, indicating fumarase isoenzymes respond dynamically to chemical stress. | DCC at 0.07 mM caused ~50% growth-rate reduction; 35 proteins changed under DCC; fumarase C among the most conspicuously decreased proteins | Quantitative proteomics of KT2440 exposed to chlorophenoxy herbicides/metabolites | Benndorf et al., 2006, *PROTEOMICS*, https://doi.org/10.1002/pmic.200500781 | (pqac-00000025) |
| Stress response / concept | Class II fumarases such as FumC are iron-independent and oxidant-resistant, providing a mechanistic rationale for fumarase C deployment when Fe–S fumarases are vulnerable. | Class II described as iron-free/oxidant-resistant; no KT2440-specific numeric values | Review/mechanistic framework for bacterial oxidative stress and fumarase class switching | Lu and Imlay, 2019, *Redox Biology*, https://doi.org/10.1016/j.redox.2019.101296 | (pqac-00000004, pqac-00000027) |
| Biochemistry / mechanism | FumC catalyzes the reversible conversion fumarate ↔ S-malate in the TCA cycle; class II fumarases are homotetrameric and iron-independent. | Fumarate affinity reported as 3.8-fold greater than for S-malate in the extracted structural/kinetic study | Structural/kinetic analysis of bacterial class II FumC (non-KT2440 homolog used for mechanistic inference) | Stuttgen et al., 2020, *FEBS Letters*, https://doi.org/10.1002/1873-3468.13603 | (pqac-00000003, pqac-00000006) |
| Metabolic engineering | In a 2024 KT2440 GSMM-guided engineering study, PP_1755/fumC2 and PP_0944/fumC1 were non-essential individually or together under tested conditions, indicating redundancy among fumarase isoenzymes. | Deletion of PP_1755 and/or PP_0944 had no impact on viability in rich or M9 p-coumarate media | Growth-coupled design for p-coumarate utilization and glutamine/indigoidine production | Banerjee et al., 2024, *bioRxiv*, https://doi.org/10.1101/2024.03.15.585139 | (pqac-00000017, pqac-00000026) |
| Metabolic engineering | The fumarase node is nevertheless critical in KT2440 aromatic carbon bioconversion; severe phenotypes emerge when the remaining dominant fumarase PP_0897 is perturbed, highlighting functional interplay with fumC isoenzymes. | Complete cutset strain failed on M9 p-coumarate agar and showed no detectable indigoidine; promoter tuning of PP_0897 gave up to 5-fold higher specific indigoidine productivity per cell and up to 2.4-fold higher glutamate pools | Genome-scale model implementation and strain engineering for p-coumarate-to-product conversion | Banerjee et al., 2024, *bioRxiv*, https://doi.org/10.1101/2024.03.15.585139 | (pqac-00000017, pqac-00000023) |
| Metabolic engineering / systems biology | FUM flux is tightly constrained for growth-coupled production from p-coumarate, showing why fumarase activity is a systems-level bottleneck even when PP_1755 itself is non-essential. | Max glutamine state: FUM 19.88 mmol/gDCW/h with 0.43 h^-1 growth; max biomass state: FUM 26.44 mmol/gDCW/h; at ~20 mmol/gDCW/h, ~0.45 h^-1 growth and 8.61 mmol/gDCW/h glutamine (0.86 mol/mol) | Proteomics-constrained modeling and experiments in engineered KT2440 | Banerjee et al., 2024, *bioRxiv*; Banerjee et al., 2025, *NPJ Systems Biology and Applications*, https://doi.org/10.1101/2024.03.15.585139; https://doi.org/10.1038/s41540-024-00480-z | (pqac-00000022, pqac-00000021) |


*Table: This table summarizes the strongest available evidence for fumarase isoenzymes in *Pseudomonas putida* KT2440, emphasizing fumC2/PP_1755 (UniProt Q88M20). It highlights identity verification, biochemical role, stress-response behavior, and recent metabolic engineering findings relevant to functional annotation.*