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

L-aspartyl-tRNAAsn:L-glutamine amido-ligase (ADP-forming)

ATP + L-aspartyl-tRNAAsn + L-glutamine + H2O = ADP + phosphate + L-asparaginyl-tRNAAsn + L-glutamate [RN:R04212];
(1a) L-glutamine + H2O = L-glutamate + NH3;
(1b) ATP + L-aspartyl-tRNAAsn = ADP + 4-phosphooxy-L-aspartyl-tRNAAsn;
(1c) 4-phosphooxy-L-aspartyl-tRNAAsn + NH3 = L-asparaginyl-tRNAAsn + phosphate

R04212
Reaction

ATP [CPD:C00002];
L-aspartyl-tRNA(Asn) [CPD:C06113];
L-glutamine [CPD:C00064];
H2O [CPD:C00001];
4-phosphooxy-L-aspartyl-tRNAAsn;
NH3 [CPD:C00014]

This reaction forms part of a two-reaction system for producing asparaginyl-tRNA in Deinococcus radiodurans and other organisms lacking a specific enzyme for asparagine synthesis. In the first step, a non-discriminating ligase (EC 6.1.1.23, aspartate---tRNAAsn ligase) mischarges tRNAAsn with aspartate, leading to the formation of aspartyl-tRNAAsn. The aspartyl-tRNAAsn is not used in protein synthesis until the present enzyme converts it into asparaginyl-tRNAAsn (aspartyl-tRNAAsp is not a substrate for this enzyme). A glutaminase subunit (cf. EC 3.5.1.2, glutaminase) produces an ammonia molecule that is transferred by a 30 A tunnel to a synthase subunit, where it is ligated to the carboxy group that has been activated by phosphorylation. Bacterial GatCAB complexes also has the activity of EC 6.3.5.7 [glutaminyl-tRNA synthase (glutamine-hydrolysing)].

EC 6.3.5.6 created 2002, modified 2012, modified 2019