Asparagine synthase (glutamine-hydrolysing) (EC 188.8.131.52, asparagine synthetase (glutamine-hydrolysing), glutamine-dependent asparagine synthetase, asparagine synthetase B, AS, AS-B) is an enzyme with systematic name L-aspartate:L-glutamine amido-ligase (AMP-forming). This enzyme catalyses the following chemical reaction
ATP + L-aspartate + L-glutamine + H2
AMP + diphosphate + L-asparagine + L-glutamate (overall reaction)
(1a) L-glutamine + H2
L-glutamate + NH3
(1b) ATP + L-aspartate + NH3
AMP + diphosphate + L-asparagine
The enzyme from Escherichia coli has two active sites6].