The coenzyme pyridoxal phosphate mediates in the catalysis of metabolic reactions of D- and L- amino acids. Although much work has been done on the mechanism of action and stereospecificity of these processes, it has been difficult to examine the intermediate stages because the substrates are processed so effectively. We therefore propose to synthesise stereospecifically labelled inhibitors of these enzymes and use them to study the overall mechanism of action of the reactions. This will involve isolation of enzyme-inhibitor complexes and trapping of enamine intermediates with thiols. The stereospecificity of formation of the Snackertz intermediate will also be studied. The use of these inhibitors will allow intimate details of the mechanism to be studied. The involvement of D-amino acids in bacterial metabolic processes makes the enzyme inhibitors of potential value as anti-bacterial drugs.