| Evidence-supported property | Specific annotation for PhaC2/Q88D23 | Key supporting sources (with year, DOI URL) |
|---|---|---|
| Gene/protein identifiers | **PhaC2 / phaC-II**, ordered locus **PP_5005**, one of two PHA polymerases in the **Pseudomonas putida KT2440** pha locus; corresponds to the target UniProt entry **Q88D23** based on consistent PP_5005 mapping in KT2440 literature. (pqac-00000001, pqac-00000003) | Mezzina et al., 2021, https://doi.org/10.1002/biot.202000165; Salvachúa et al., 2020, https://doi.org/10.1111/1751-7915.13481 |
| Enzyme class | **Class II PHA synthase / polymerase** involved in **medium-chain-length (mcl)-PHA** biosynthesis. (pqac-00000000, pqac-00000001) | Vilchis, 2024; Mezzina et al., 2021, https://doi.org/10.1002/biot.202000165 |
| Catalytic reaction | Catalyzes polymerization of **(R)-3-hydroxyacyl-CoA** monomers into intracellular **mcl-PHA** polyester granules; literature places PhaC2 in the polymerization step of the peripheral PHA pathway. (pqac-00000001, pqac-00000002, pqac-00000004) | Mezzina et al., 2021, https://doi.org/10.1002/biot.202000165; Manoli et al., 2022, https://doi.org/10.1128/mbio.01794-21; Salvachúa et al., 2020 Fig. 1, https://doi.org/10.1111/1751-7915.13481 |
| Substrate specificity/range | Evidence supports use of **(R)-3-hydroxyacyl-CoA** substrates from the **mcl** pool; KT2440 mcl-PHA compositions reported in pathway reviews span roughly **C6-C14** monomers depending on carbon source, but direct KT2440 PhaC2-only kinetic specificity was **not** extracted from the gathered snippets. (pqac-00000001, pqac-00000002) | Mezzina et al., 2021, https://doi.org/10.1002/biot.202000165; Manoli et al., 2022, https://doi.org/10.1128/mbio.01794-21 |
| Pathway context (β-oxidation vs de novo FA via PhaG/AlkK) | PhaC2 acts downstream of two monomer-supply routes: **β-oxidation**, which generates (R)-3-hydroxyacyl-CoA intermediates from fatty acids, and **de novo fatty-acid synthesis**, where **PhaG** converts (R)-3-hydroxyacyl-ACP to (R)-3-hydroxyfatty acid and **AlkK** ligates this to **(R)-3-hydroxyacyl-CoA**, the substrate polymerized by PhaC. (pqac-00000003, pqac-00000004, pqac-00000001) | Salvachúa et al., 2020, https://doi.org/10.1111/1751-7915.13481; Mezzina et al., 2021, https://doi.org/10.1002/biot.202000165 |
| Cellular localization | PhaC2 belongs to the **granule-associated protein (GAP)** set that coats **cytoplasmic PHA storage granules** in P. putida; this supports intracellular localization at the PHA granule surface rather than secretion or membrane transport function. (pqac-00000002) | Manoli et al., 2022, https://doi.org/10.1128/mbio.01794-21 |
| Regulation/physiological role | PhaC2 functions in the **PHA cycle**, a dynamic synthesis/degradation system linked to central carbon metabolism and metabolic robustness. PHA accumulation is associated with **carbon excess and nutrient limitation** (e.g., N or P limitation), placing PhaC2 in carbon-storage and stress-adaptation physiology. (pqac-00000002) | Manoli et al., 2022, https://doi.org/10.1128/mbio.01794-21 |
| Engineering/phenotype quantitative data | In a KT2440 engineering study, **overexpression of phaC2 together with phaG, alkK, and phaC1** plus deletions in **phaZ, fadBA1, fadBA2** increased mcl-PHA performance versus wild type by **53% (p-coumaric acid) and 200% (lignin) in titer**, and **20% and 100% in yield**, respectively; this supports PhaC2 as a productive polymerase target, although the effect is from a multi-gene intervention rather than isolated phaC2 overexpression. (pqac-00000003) | Salvachúa et al., 2020, https://doi.org/10.1111/1751-7915.13481 |


*Table: This table summarizes evidence-supported functional annotation for Pseudomonas putida KT2440 PhaC2 (phaC-II; PP_5005; UniProt Q88D23). It highlights identity, catalytic role, pathway context, localization, and quantitative engineering evidence using only the gathered sources.*