N-Acetyl-L-arginine (Ac-Arg-OH) belongs to the class of organic compounds known as n-acyl-l-alpha-amino acids. These are n-acylated alpha amino acids which have the L-configuration of the alpha-carbon atom. N-a-Acetyl-L-arginine serum levels (and other guanidino compounds) were elevated of all the hyperargininemic patients are higher than the normal range. N-a-Acetyl-L-arginine is a very strong basic compound (based on its pKa). Untreated hyperargininemic patients have the highest guanidino compound levels in cerebrospinal fluid. N-a-Acetyl-L-arginine is one of the guanidino compounds found elevated in the serum of an hemodialyzed renal insufficient (uremic) pediatric population. Outside of the human body, N-a-Acetyl-L-arginine has been detected, but not quantified in, apples and loquats. This could make N-a-acetyl-L-arginine a potential biomarker for the consumption of these foods. N-a-Acetyl-L-arginine, with regard to humans, has been found to be associated with several diseases such as uremia and colorectal cancer; N-a-acetyl-L-arginine has also been linked to the inborn metabolic disorder hyperargininemia. During a low-arginine diet, together with sodium benzoate therapy, there was a marked decrease in plasma N-alpha-acetylarginine. N-a-Acetyl-L-arginine increases in urine hyperargininemic patients.