asparagina

Asparagina, known in English as asparagine, is an α-amino acid that is polar and uncharged at physiological pH. It is one of the 20 standard amino acids used to build proteins and is considered non-essential in humans, since the body can synthesize it.

Its side chain is a methylene group linked to an amide, giving the structure -CH2-CONH2. The molecule has the formula C4H8N2O3. In proteins, the L-enantiomer is incorporated by ribosomes. It is water-soluble and neutral at physiological pH, with hydrogen-bonding capacity from its amide group.

Biosynthesis and metabolism: Asparagine is produced from aspartate by asparagine synthetase (ASNS) in an ATP-dependent reaction, using ammonia or glutamine as the nitrogen donor.

Biological roles: In proteins, asparagine residues are sites of N-linked glycosylation, important for folding and stability of many secreted and membrane proteins. It also participates in nitrogen transport in plants. The amino acid can be deamidated to aspartate by asparaginase, linking its metabolism to central pathways.

Clinical and dietary notes: L-asparaginase is used to treat acute lymphoblastic leukemia by depleting extracellular asparagine. Deficiency of asparagine synthetase (ASNSD) is a rare genetic disorder with neurodevelopmental features. Dietary sources include dairy, eggs, meat, and legumes.

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