Asymmetric dimethylarginine (ADMA) is a naturally occurring chemical found in blood plasma. It is a metabolic by-product of continual protein modification processes in the cytoplasm of all human cells. It is closely related to L-arginine, a conditionally-essential amino acid. ADMA interferes with L-arginine in the production of nitric oxide, a key chemical to endothelial and hence cardiovascular health. Asymmetric dimethylarginine is created in protein methylation, a common mechanism of post-translational protein modification. This reaction is catalyzed by an enzyme set called S-adenosylmethionine protein N-methyltransferases (protein methylases I and II). The methyl groups transferred to create ADMA are derived from the methyl group donor S-adenosylmethionine, an intermediate in the metabolism of homocysteine. (Homocysteine is an important blood chemical, because it is also a marker of cardiovascular disease). After synthesis, ADMA migrates into the extracellular space and thence into blood plasma. Asymmetric dimethylarginine is measured using high performance liquid chromatography. ADMA has been identified as a uremic toxin according to the European Uremic Toxin Working Group.