Figure 1.

Overview of mammalian arginine metabolism. Sources of the free arginine pool are indicated, as well as the various end products of arginine metabolism. In addition to arginine, the methylated arginine derivatives asymmetric dimethyl-L-arginine (ADMA), symmetric dimethyl-L-arginine (SDMA) and N^G-monomethyl-L-arginine (NMMA) are released upon the turnover of post-translationally methylated proteins. Enzymes that use arginine as substrate are: (a) arginyl-tRNA synthetase; (b) NO synthases; (c) arginases; (d) arginine:glycine amidinotransferase; and (e) arginine decarboxylase. Not shown are the various transporters that are required for movement of arginine across plasma and mitochondrial membranes.