asparagine synthase (glutamine-hydrolysing);
asparagine synthetase (glutamine-hydrolysing);
glutamine-dependent asparagine synthetase;
asparagine synthetase B;
AS;
AS-B

Ligases;
Forming carbon-nitrogen bonds;
Carbon-nitrogen ligases with glutamine as amido-N-donor

L-aspartate:L-glutamine amido-ligase (AMP-forming)

ATP + L-aspartate + L-glutamine + H2O = AMP + diphosphate + L-asparagine + L-glutamate (overall reaction) [RN:R00578];
(1a) L-glutamine + H2O = L-glutamate + NH3 [RN:R00256];
(1b) ATP + L-aspartate + NH3 = AMP + diphosphate + L-asparagine [RN:R00483]

R00256 R00483 R00578

ATP [CPD:C00002];
L-aspartate [CPD:C00049];
L-glutamine [CPD:C00064];
H2O [CPD:C00001];
NH3 [CPD:C00014]

The enzyme from Escherichia coli has two active sites [4] that are connected by an intramolecular ammonia tunnel [5,6]. The enzyme catalyses three distinct chemical reactions: glutamine hydrolysis to yield ammonia takes place in the N-terminal domain. The C-terminal active site mediates both the synthesis of a beta-aspartyl-AMP intermediate and its subsequent reaction with ammonia. The ammonia released is channeled to the other active site to yield asparagine [6].