In enzymology, an aspartateâÂÂammonia ligase () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are ATP, L-aspartate, and NH<sub>3</sub>, whereas its 3 products are AMP, diphosphate, and L-asparagine.
This enzyme belongs to the family of ligases, specifically those forming carbon-nitrogen bonds as acid-D-ammonia (or amine) ligases (amide synthases). The systematic name of this enzyme class is L-aspartate:ammonia ligase (AMP-forming). Other names in common use include asparagine synthetase, and L-asparagine synthetase. This enzyme participates in 3 metabolic pathways: alanine and aspartate metabolism, cyanoamino acid metabolism, and nitrogen metabolism.
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and .