Design, Synthesis and Characterisation of Inhibitors of 3-Deoxy-D-arabino-Heptulosonate 7-Phosphate Synthase
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The enzyme 3-deoxy D-arabino-heptulosonate 7-phosphate (DAH7P) synthase catalyses the first step of the shikimate pathway. This pathway lies at the heart of bacterial metabolism, and is responsible for the synthesis of a variety of compounds essential to the chemistry of life; from the aromatic amino acids phenylalanine, tyrosine and tryptophan, to a number of aromatic and non-aromatic natural products. This thesis describes the design, synthesis and evaluation of inhibitors of DAH7P synthase. These inhibitors exploit a variety of strategies to interrupt the activity of DAH7P synthase, ranging from simple substrate mimicry to inhibitors that mimic unstable reaction intermediates; inhibitors that exploit metal coordination and entropic effects, and inhibitors that gain improved potency by interacting with multiple sites. In Chapter Two, the synthesis of a mimic for a proposed unstable reaction intermediate is described, and its interaction with DAH7P synthase characterised. The compound was prepared in twelve steps from D-arabinose, and was found to be a slow-tight binding inhibitor of Escherichia coli DAH7P synthase. In Chapter Three, a number of compounds are prepared that were designed to bind to the phosphoenolpyruvate subsite of the DAH7P synthase active site. The binding of these compounds to the enzyme is investigated in order to gain an understanding of the factors involved in DAH7P synthase inhibition. The enantiomeric phospholactates were prepared, and the extent of inhibition of E. coli DAH7P synthase was shown to be dependent on compound chirality. Several other phosphoenolpyruvate-like molecules were prepared, and were also shown to be effective DAH7P synthase inhibitors. In Chapter Four extended compounds are designed that will bind the enzyme by multiple interactions at both substrate binding sites. Four compounds were prepared, and an increase in inhibitory potency was observed. In Chapter Five computational techniques are explored to aid the interpretation of the inhibition of DAH7P synthase by the compounds prepared in these studies. Several approaches for more potent inhibition of this enzyme are outlined and discussed.