| Aspect | Key findings | Evidence type | Best citations |
|---|---|---|---|
| Identity | PP_4678 in *Pseudomonas putida* KT2440 is annotated as **ilvC**, encoding ketol-acid reductoisomerase/acetohydroxyacid isomeroreductase (KARI/AHAIR; EC 1.1.1.86). Independent *P. putida* engineering studies place native ilvC in the ilvCD locus used for branched-chain ketoacid formation, matching UniProt Q88DZ0. | Experimental, engineering, inference | (pqac-00000001, pqac-00000017) |
| Reaction | IlvC/KARI catalyzes the coupled **isomerization plus reduction** step of branched-chain amino-acid biosynthesis, converting AHAS products toward dihydroxy-acid intermediates on the route to 2-ketoisovalerate and related branched-chain precursors. | Experimental, inference | (pqac-00000004, pqac-00000009) |
| Substrates/cofactors | Physiological substrates include acetolactate/acetohydroxybutyrate pathway intermediates; assays for bacterial IlvC use α-acetolactate as substrate and monitor **NADPH** oxidation. KARI generally requires a divalent metal ion, usually **Mg²⁺**, for the alkyl-migration step. | Experimental, inference | (pqac-00000003, pqac-00000010, pqac-00000011) |
| Pathway role | IlvC is the second step in the pyruvate-to-2-ketoisovalerate segment of **branched-chain amino-acid biosynthesis**. It supports synthesis of valine and isoleucine directly and leucine indirectly via 2-oxoisovalerate-derived metabolism. | Experimental, inference | (pqac-00000009, pqac-00000015) |
| Localization | No direct localization study was found for *P. putida* IlvC, but bacterial IlvC/AHAIR is characterized as a **soluble/cytosolic** enzyme in related Gram-negative bacteria, with purification from soluble lysate and no detergent requirement; this supports a cytosolic localization inference for KT2440 IlvC. | Experimental in homolog, inference for *P. putida* | (pqac-00000012, pqac-00000011) |
| Genetics/phenotype in *P. putida* | In a genome-wide mutant screen, **ilvC (PP4678)** was identified as conditionally essential for growth on glucose minimal medium. *ilvC* mutants showed branched-chain amino-acid auxotrophy, with reported requirements involving isoleucine and valine/leucine supplementation depending on the assay context. | Experimental genetics | (pqac-00000017, pqac-00000015, pqac-00000016) |
| Engineering applications | Native *P. putida* **ilvC** has been repeatedly overexpressed with **ilvD** (and often **alsS**) to channel pyruvate into 2-ketoisovalerate and isobutanol production. Recent KT2440 work also embeds ilvC in tunable metabolic-valve designs that connect growth control with ketoacid overproduction. | Engineering | (pqac-00000000, pqac-00000013, pqac-00000014) |
| Quantitative data | Engineered *P. putida* KT2440 strains overexpressing native **ilvC/ilvD** produced isobutanol at **22 ± 2 mg/g glucose** aerobically, while microaerobic processing improved glucose-to-isobutanol yield to **60 mg/g glucose** and a 30 L process reached **3.35 g/L**. For a characterized bacterial IlvC homolog, reported kinetics include **K\_M ~6.2 mM** for α-acetolactate, **K\_M 12.5 µM** for NADPH, and **V\_max 191 ± 3 mU/mg**. | Engineering, experimental biochemistry | (pqac-00000000, pqac-00000005, pqac-00000007) |


*Table: This table summarizes the main functional annotation evidence for *Pseudomonas putida* KT2440 ilvC (Q88DZ0/PP_4678), including biochemical role, pathway context, localization inference, genetics, and engineering relevance. It is useful as a compact evidence map linking species-specific findings to broader KARI knowledge.*