Rational modulation of enzyme flexibility: a new approach in enzyme engineering for green chemistry

Galactokinase is a metabolic enzyme which catalyses the formation of galactose 1-phosphate from galactose and ATP. Sugar phosphates are important precursors in the synthesis of a number of important molecules, including aminoglycoside antibiotics. Their chemical synthesis is difficult and requires the use of harmful solvents and reagents. A biocatalytic approach would remove the need for these reagents while also enhancing yield and purity. However, enzymes are generally highly specific and only catalyse reactions of limited range of substrates. The specificity of human galactokinase has recently been relaxed through site-directed mutagenesis, albeit in a way which results in substantial loss of activity (work funded by the EPA’s Green Chemistry initiative as part of the STRIVE programme). This work suggested that increased protein flexibility was a key factor in altering the specificity and that further improvements could be made with a greater understanding of the dynamics of the enzyme. Therefore, the student will:

1. Carry out computational simulations of the dynamics of galactokinase (both wild type and specificity-relaxed mutants) to understand how flexibility influences catalysis and specificity

2. Test predictions from this modelling using site-directed mutagenesis and biochemical experiments which probe the influence of flexibility

3. Use a combined computational and experimental approach to “design in” altered flexibility in a way which is predicted to extend the specificity of the enzyme so that it will catalyse the phosphorylation of substrates of commercial interest.

This project will be supervised by Dr David Timson of the School of Biological Sciences and Dr Meilan Huang of the School of Chemistry and Chemical Engineering.