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Engineering the substrate specificity of xylose isomerase
Johanna Karimäki1, Tarja Parkkinen, Harri Santa
1Laboratory of Bioprocess Engineering, Helsinki University of Technology, PO Box 6100, 02015-HUT and Department of Chemistry, University of Joensuu, PO Box 111, 80101 Joensuu, Finland.
Protein Engineering, Design & Selection : PEDS
|February 17, 2005
Summary
Xylose isomerase (XI) engineering improved L-arabinose processing. Mutations enhanced enzyme efficiency by altering substrate binding and active site properties, demonstrating potential for tailored enzyme specificity.
Area of Science:
- Biochemistry
- Enzyme engineering
- Structural biology
Background:
- Xylose isomerase (XI) catalyzes sugar isomerization and epimerization.
- Low efficiency with L-arabinose necessitates structural and engineering studies.
Purpose of the Study:
- Determine the structural basis for low L-arabinose efficiency in XI.
- Engineer XI variants with improved catalytic efficiency for L-arabinose.
Main Methods:
- Crystal structure determination of Streptomyces rubiginosus XI complexed with L-arabinose.
- Site-directed mutagenesis of Actinoplanes missouriensis XI.
- Free energy perturbation simulations.
- Enzyme activity assays.
Main Results:
- L-arabinose binds differently in the active site compared to other sugars, hindering catalytic metal M2 interaction.
- Mutation F26W increased XI catalytic efficiency 2-fold, primarily in kcat, by repositioning L-arabinose.
- Mutation Q256D improved XI catalytic efficiency 3-fold (kcat and Km) by altering active site electrostatics.
Conclusions:
- Structural insights reveal L-arabinose binding challenges in XI.
- Enzymatic engineering can significantly enhance XI's efficiency with L-arabinose.
- Tailoring XI substrate specificity is achievable through targeted mutations.