Amino Acids Can Be Classified into Groups on the Basis of Metabolic Characteristics

The discussion of amino acid absorption and metabolism becomes complicated because not all amino acids are subject

U-Ketoglutarate

FIGURE 32-6 ■ Example of amino acids and their keto-analogues.

to the same reactions. For this discussion the amino acids arc divided into two groups, each containing two subgroups (Table 32-1). The major groups are the “nutritionally dis­pensable” amino acids and the “nutritionally indispensable” amino acids. Within the dispensable amino acid group, glu­tamate, aspartate, and alanine are separated out as transport amino acids; within the indispensable amino acid group, leucine, isoleucine, and valine form a special subgroup known as the branch-chain amino acids (BCAAs). The transport amino acids are utilized in several reactions in which amino groups are transferred from molecule to molecule or organ to organ.