ABSTRACT
The importance of the branched-chain amino acids-valine, leucine, and isoleucine-as building blocks of proteins in plants is obvious. In addition, several secondary plant products are derived from these amino acids (see Chap. 1). Also, the intennediates of the branched-chain amino acid biosynthetic pathway are used in the biosynthesis of pantothenate and propionyl-CoA. Because mammals do not synthesize these amino acids. their biosynthesis in plants is of special interest. In addition, the discovery of four different classes of commercial herbicides that inhibit their biosynthesis (see Chap. 14) has called much attention to this pathway. These herbicides are unique in the range of weeds they control, the range of crops in which they are used. their low use rates. and their favorable environmental properties. The discovery and development of these herbicides and of crops resistant to them has led to an explosion in the scientific literature on biochemical, molecular, and genetic aspects of plant branched-chain amino acid biosynthesis. Increased research in this field is reflected by the progress made since the last review on this pathway by Wallsgrove (1990) and Bryan (1990).
