2004 by CRC Press LLC. L -Arginine (2-amino-5-guanidinovaleric acid) is an amino acid with remarkable metabolic and regulatory versatility. In 1988, it was identified as the physiological precursor for the synthesis of nitric oxide (NO) in animal cells (Table 10.1).1,2 The discovery of NO synthesis has stimulated an enormous interest in arginine metabolism over the past decade. Thus, much effort has been directed to explore nutritional or therapeutic roles of arginine to treat many human diseases that are associated with a relative or absolute deficiency of arginine or with a reduced bioavailability of NO3-5 (see Chapter 35). However, it should be borne in mind that other aspects of arginine metabolism in addition to NO synthesis play very important physiological roles. These include the synthesis of arginine itself, as well as the catabolism of arginine to produce compounds such as proline, polyamines (putrescine, spermidine, and spermine), creatine, agmatine, and glutamate (Figure 10.1).
