Recombinant Serine acetyltransferase (cysE)
Description
Definition and Biological Role
Recombinant CysE is produced through heterologous expression systems (e.g., Escherichia coli) to study its enzymatic properties or develop therapeutic inhibitors. It is essential for microbial survival, particularly in pathogens like Mycobacterium tuberculosis and E. coli, where cysteine biosynthesis is vital for antioxidant defense and virulence .
Enzymatic Activity and Kinetics
Recombinant CysE exhibits species-specific catalytic properties:
Table 1: Kinetic Parameters of Recombinant CysE
| Source | Specific Activity (μmol/min/mg) | K<sub>m</sub> (L-Ser) | K<sub>m</sub> (Acetyl-CoA) | Optimal pH | Optimal Temp (°C) |
|---|---|---|---|---|---|
| E. coli | 71.6 | 1.17 mM | 0.2 mM | 7.5 | 25 |
| M. tuberculosis | 10.66 | 0.026 mM | 0.051 mM | 7.5 | 37 |
| Engineered E. coli (CysE-C) | 35.1 | N/A | N/A | 7.5 | 37 |
M. tuberculosis CysE shows a 40-fold higher affinity for L-serine than E. coli CysE, suggesting evolutionary adaptations to substrate availability .
Regulation and Inhibition
CysE activity is feedback-inhibited by cysteine, but sensitivity varies:
Inhibitor Studies
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Alkyl gallates (e.g., octyl gallate): Bind to the acetyl-CoA site, reducing OAS synthesis and depleting bacterial cysteine levels (IC<sub>50</sub> = 250 μM for E. coli) .
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Methionine-substituted variants: Engineered CysE-CM retains 10% activity, demonstrating tolerance to sulfur starvation .
Therapeutic Potential
Recombinant CysE is pivotal in drug discovery:
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Antimicrobial Targets: CysE inhibitors sensitize drug-resistant Klebsiella pneumoniae and E. coli to carbapenems by disrupting redox balance .
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High-Throughput Screening: M. tuberculosis CysE’s resolved kinetics enable rapid inhibitor testing .
Research Challenges and Future Directions
Product Specs
Target Background
KEGG: mtu:Rv2335
STRING: 83332.Rv2335
