Recombinant Branched-chain-amino-acid aminotransferase (ilvE)
Description
Mechanistic Insights
IlvE follows a ping-pong kinetic mechanism involving two half-reactions :
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Amino Group Transfer: PLP-bound enzyme reacts with L-glutamate, forming α-ketoglutarate and pyridoxamine 5′-phosphate (PMP).
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BCAA Synthesis: PMP donates the amino group to α-keto acids (e.g., α-ketoisovalerate), regenerating PLP and producing BCAAs.
Key mechanistic observations:
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pH Sensitivity: Activity depends on protonation states of PLP phosphate (pKa ~6.5) and Lys204 (pKa ~8.5) .
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Kinetic Isotope Effects: Primary deuterium isotope effects (Dk) indicate concerted C–H bond cleavage and proton transfer during catalysis .
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Substrate Broadness: M. tuberculosis IlvE also processes aromatic amino acids (e.g., phenylalanine) .
BCFA Synthesis and Membrane Integrity
In Listeria monocytogenes:
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IlvE supplies isoleucine-derived anteiso-branched-chain fatty acids (ai-BCFAs), constituting >60% of membrane lipids .
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ΔilvE mutants exhibit:
Virulence and Stress Resistance
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Intracellular Survival: IlvE-deficient L. monocytogenes shows 66% reduced cell-to-cell spread and attenuated mouse virulence .
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Acid Resistance: In Streptococcus mutans, IlvE links BCAA metabolism to branched-chain fatty acid production, enhancing acid tolerance .
Table 2: Phenotypic Consequences of IlvE Deficiency
| Organism | Phenotype | Reference |
|---|---|---|
| L. monocytogenes | Reduced ai-BCFAs, membrane stress sensitivity | |
| M. tuberculosis | Disrupted methionine salvage pathway | |
| S. mutans | Acid sensitivity, BCAA auxotrophy |
Biotechnological and Therapeutic Applications
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Drug Target: IlvE inhibitors (e.g., aminooxy compounds) block BCAA biosynthesis in M. tuberculosis, impairing growth .
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Recombinant Production: Overexpression in E. coli enables structural studies and high-throughput inhibitor screening .
Research Gaps and Future Directions
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Structural Dynamics: How oligomeric states influence substrate specificity.
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Host-Pathogen Interactions: Role of IlvE in evading host immune responses.
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Inhibitor Optimization: Developing species-selective inhibitors to minimize off-target effects.
Product Specs
Target Background
KEGG: ece:Z5281
STRING: 155864.Z5281
