History

Asparagine was first isolated in 1806 from asparagus juice, in which it is abundant -- hence its name -- becoming the first amino acid to be isolated. The characteristic smell observed in the urine of individuals after their consumption of asparagus is attributed to various metabolic byproducts of asparagine.

Structural function in proteins

Since the asparagine side chain can form hydrogen bond interactions with the peptide backbone, asparagine residues are often found near the beginning and the end of alpha-helices, and in turn motifs in beta sheets. Its role can be thought as "capping" the hydrogen bond interactions which would otherwise be satisfied by the polypeptide backbone. Glutamines, with an extra methylene group, have more conformational entropy and thus are less useful in this regard. Asparagine also provides key sites for N-linked glycosylation, modification of the protein chain with the addition of carbohydrate chains.

Dietary Sources

Asparagine is not an essential amino acid, which means that it can be synthesized from central metabolic pathway intermediates in humans and is not required in the diet. Asparagine is found in: Animal sources: dairy, whey, beef, poultry, eggs, fish, lactalbumin, seafood Vegetarian sources: asparagus, potatoes, legumes, nuts, seeds, soy, whole grains