The 3-phenylpropionate catabolic pathway found in Escherichia coli is a member of the family of oxidative meta-cleavage pathways employed by bacteria in the degradation of aromatic molecules. The enzyme 2-hydroxy penta-2,4-dienoic acid hydratase (MhpD) catalyses the hydration of 2-hydroxy penta-2,4-dienoic acid (16) to afford 4-hydroxy-2-keto pentanoic acid. This is then cleaved in a retro-aldol reaction catalysed by 4-hydroxy-2-keto pentanoic acid aldolase (MhpE), to yield pyruvic acid and acetaldehyde. This thesis describes the studies toward the purification and characterisation of the enzymes MhpD and MhpE and the characterisation of the two reactions catalysed. The mechanism of the MhpD catalysed reaction was probed using analogues of possible reaction intermediates as potential inhibitors. Sodium oxalate was found to act as a potent inhibitor with a K₁ of 4.9 μM. Inhibition by oxalate is consistent with a mechanism in which tautomerisation to 2-keto pent-3-enoic acid takes place at the enzyme active site, followed by conjugate addition of water to afford an enolate intermediate. Stereochemistry at C-5 was studied using a chiral methyl strategy.