Arginine (Arg) is a conditionally essential amino acid that plays
key roles in nitrogen metabolism and ureagenesis, in cellular multiplication,
in energy metabolism, and in endothelial function. In healthy
adults, besides adaptation to its dietary supply, Arg homeostasis depends on its synthesis
thanks to a gut–kidney cooperation and on its recycling from citrulline. If quantitatively its most
important use is protein synthesis, qualitatively,
its role as precursor of nitric oxide (°NO) and polyamines is crucial.