Metabolic and performance benefits of L-Arginine over Guanidinoacetic acid

IntroductionThere are at least five commercially available synthetic amino acids, namely methionine, lysine, threonine, tryptophan and valine. Currently, arginine (Arg) is available which is produced through bio-fermentation. L-Arg is an essential amino acid for chickens due to unavailability of two separate enzymes in urea cycle in the kidney and almost all urea cycle enzymes in the liver (Leeson and Summers, 2001). The mammalian cells have a fully functional urea cycle. Therefore, L-Arg is not considered as an essential amino acid in swine. However, new data shows that endogenous arginine synthesis through urea cycle is not enough to cover arginine requirements in swine (Wu et al., 2007). Thus, arginine is named to be essential e.g. in piglets as well.Guanidinoacetic acid (GAA) is the precursor of creatine which is synthesized via a two steps process involving two enzymes and three amino acids: arginine, glycine, and methionine. In the first step, arginine : glycine amidinotransferas...