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Updated: Jul 6, 2026

A New Screening Method for the Directed Evolution of Thermostable Bacteriolytic Enzymes
Published on: November 7, 2012
Directed evolution of transketolase substrate specificity towards an aliphatic aldehyde
Edward G Hibbert1, Tarik Senussi, Mark E B Smith
1Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, Torrington Place, London WC1E 7JE, UK.
Directed evolution created transketolase (TK) mutants with enhanced specificity for propionaldehyde. Mutations at conserved residues improved activity on non-natural substrates, guiding enzyme engineering for specific applications.
Area of Science:
- Biochemistry
- Enzyme Engineering
- Directed Evolution
Background:
- Transketolase (TK) is a key enzyme in the pentose phosphate pathway.
- Natural TK substrates are C2-hydroxylated aldehydes.
- Engineering TK for non-natural substrates presents a significant challenge.
Purpose of the Study:
- To obtain transketolase (TK) mutants with improved specificity for the non-natural aliphatic aldehyde propionaldehyde.
- To compare mutations conferring specificity for natural versus non-natural substrates.
- To guide directed evolution strategies for enzyme engineering.
Main Methods:
- Utilized active-site targeted saturation mutagenesis libraries.
- Employed directed evolution to screen for improved substrate specificity.
- Compared enzyme activity and specificity of novel mutants against natural substrates.
Main Results:
- Identified distinct sets of active-site mutations for improved overall activity versus substrate specificity.
- Mutants at conserved residues showed up to 5-fold improvement in specific activity for propionaldehyde.
- Achieved a 64-fold improvement in specificity towards propionaldehyde compared to glycolaldehyde.
Conclusions:
- Saturation mutagenesis can be selectively guided towards natural or non-natural substrates.
- Mutations at conserved residues interacting with the C2-hydroxyl group are key for non-natural substrate specificity.
- This work provides insights into engineering enzyme specificity for novel applications.
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