| Category | Key facts | Organism/Scope | Evidence source (with DOI URL and year) |
|---|---|---|---|
| Verified identity | User-specified target is **hisC / PP_0967 / UniProt Q88P86** in *Pseudomonas putida* KT2440. KT2440 histidine-biosynthesis genes are organized in four clusters, and **PP0965–PP0967** is annotated as the **hisGDC** cluster, placing **PP_0967 as hisC** in this strain-specific genomic context; this matches the expected role of histidinol-phosphate aminotransferase in histidine biosynthesis. Generic histidine-pathway references also identify **HisC = histidinol aminotransferase, EC 2.6.1.9**. (pqac-00000000, pqac-00000010) | *P. putida* KT2440 for locus/operon context; broad bacterial annotation for enzyme name/EC | Molina-Henares et al., 2010, *Environmental Microbiology*, DOI: https://doi.org/10.1111/j.1462-2920.2010.02166.x; Winkler & Ramos-Montañez, 2009, *EcoSal Plus*, DOI: https://doi.org/10.1128/ecosalplus.3.6.1.9 |
| Catalyzed reaction and pathway step | **HisC (EC 2.6.1.9)** catalyzes the **7th step of histidine biosynthesis**: amino-group transfer from **L-glutamate** to **imidazole acetol-phosphate / 3-(imidazol-4-yl)-2-oxo-propyl phosphate**, producing **L-histidinol phosphate** and **2-oxoglutarate (α-ketoglutarate)**. The transferred amino group becomes the product’s α-amino group. (pqac-00000003, pqac-00000005, pqac-00000006, pqac-00000007) | Broad bacterial HisC biochemistry and structural enzymology | Sivaraman et al., 2001, *J. Mol. Biol.*, DOI: https://doi.org/10.1006/jmbi.2001.4882; Matte et al., 2003, *J. Bacteriol.*, DOI: https://doi.org/10.1128/jb.185.14.3994-4002.2003; Winkler & Ramos-Montañez, 2009, *EcoSal Plus*, DOI: https://doi.org/10.1128/ecosalplus.3.6.1.9; Fernandez et al., 2004, *J. Biol. Chem.*, DOI: https://doi.org/10.1074/jbc.m400291200 |
| Mechanistic/structural features | HisC is a **PLP-dependent aminotransferase** that follows a **ping-pong (double-displacement)** mechanism. Structural work shows a **dimeric enzyme (~80 kDa total in *E. coli*)**, with each monomer containing a **large PLP-binding domain**, a **smaller domain**, and an **N-terminal arm** involved in dimerization/active-site shielding. The catalytic **Lys214** (numbering from *E. coli* HisC) forms the **internal aldimine** with PLP; crystallography captured **PMP**, **internal aldimine**, and a **covalent tetrahedral/gem-diamine-like intermediate** with PLP and L-histidinol phosphate. Conserved PLP-interacting residues include **Tyr55, Asn157, Asp184, Tyr187, Ser213, Lys214, Arg222**. (pqac-00000003, pqac-00000004, pqac-00000005, pqac-00000006, pqac-00000008, pqac-00000009, pqac-00000015) | Broad bacterial HisC structural mechanism; residue numbering from *E. coli* and *Thermotoga maritima* homologs used for functional inference | Sivaraman et al., 2001, *J. Mol. Biol.*, DOI: https://doi.org/10.1006/jmbi.2001.4882; Matte et al., 2003, *J. Bacteriol.*, DOI: https://doi.org/10.1128/jb.185.14.3994-4002.2003; Fernandez et al., 2004, *J. Biol. Chem.*, DOI: https://doi.org/10.1074/jbc.m400291200 |
| KT2440 genomic context / operon evidence | In *P. putida* KT2440, histidine biosynthesis genes occur in **four genomic clusters**. One cluster is **PP0965–PP0967 (hisGDC)**, and RT-PCR evidence indicated these histidine clusters form **independent operons**, supporting that **hisC/PP_0967 is cotranscribed with neighboring histidine-biosynthesis genes** in this region. A separate monocistronic **hisZ** locus is **PP4890**. (pqac-00000000) | *P. putida* KT2440 | Molina-Henares et al., 2010, *Environmental Microbiology*, DOI: https://doi.org/10.1111/j.1462-2920.2010.02166.x |
| KT2440 functional genomics / essentiality | In a genome-wide miniTn5 screen of **7,760** KT2440 mutants, **79** mutants failed to grow on glucose minimal medium, mapping to **47–48 conditionally essential genes**; histidine auxotrophs were recovered, including **hisB (PP0289), hisF (PP0293), hisH (PP0290), and hisZ (PP4890)**, but **no hisC mutant was recovered**, so this study supports histidine-pathway importance in minimal medium without direct knockout evidence for **PP_0967**. A 2024 RB-TnSeq/ICA reanalysis identified histidine-related functional modules (e.g., **hisA in fModule_71**, “His metabolism” connection to **HutC** iModulon), but the cited text provides **no quantitative hisC-specific fitness value or essentiality call**. (pqac-00000011, pqac-00000012, pqac-00000013, pqac-00000014) | *P. putida* KT2440 functional genomics | Molina-Henares et al., 2010, *Environmental Microbiology*, DOI: https://doi.org/10.1111/j.1462-2920.2010.02166.x; Borchert et al., 2024, *mSystems*, DOI: https://doi.org/10.1128/msystems.00942-23 |


*Table: This table consolidates strain-specific identity and operon evidence for PP_0967/hisC in Pseudomonas putida KT2440 with core biochemical and structural knowledge for HisC enzymes. It also distinguishes direct KT2440 evidence from broader homolog-based inference and notes current limits of hisC-specific functional-genomics data.*