Understanding the Relationship Between Enzyme Structure and Catalysis

The three dimensional structure of an enzyme is of fundamental importance to almost every function it performs. In this thesis, we aim to analyse the structures of many enzymes in order to gain insights into how they perform catalysis, and the role of structure in enzyme function. As well as improving our understanding of these important biological molecules, these insights will help in developing new tools for annotating enzyme structures of unknown function and for designing novel enzymes. Predicting the location of the active site, and the identity of the catalytic residues, is an important first step for annotating an enzyme of unknown function. We have developed a neural network trained to distinguish catalytic and non-catalytic residues based on a mixture of sequence and structural parameters. We find that the correct location of the active site can be predicted in ∼70% of cases. We also find that the most important factor in making a prediction is the conservation score of each residue. However, including structural data does improve the predictions that are made over those made on the basis of conservation alone. Our first analysis of enzyme structure aims to measure the extent of conformational change undergone upon substrate binding. We find that most enzymes do not undergo large scale conformational change, and in many cases the catalytic residues are isolated from changes that do occur. One new theory of enzyme action suggests that certain, very small, conformational changes (deriving from changes in the en-