The central enzymes of the aspartate family of amino acid biosynthesis

The aspartate pathway is responsible for the biosynthesis of lysine, threon ine, isoleucine, and methionine in most plants and micro-organisms. The abs ence of this pathway in humans and animals makes the central enzymes potent ial targets for inhibition, with the aim of developing new herbicides and b iocides, and also for enhancement, to improve the nutritional value of crop s. Our current state of knowledge of these enzymes is reviewed, including r ecently determined structural information and newly constructed bifunctiona l fusion enzymes.