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

L-glutamyl-tRNAGln:L-glutamine amido-ligase (ADP-forming)

ATP + L-glutamyl-tRNAGln + L-glutamine = ADP + phosphate + L-glutaminyl-tRNAGln + L-glutamate (overall reaction) [RN:R03905];
(1a) L-glutamine + H2O = L-glutamate + NH3;
(1b) ATP + L-glutamyl-tRNAGln = ADP + 5-phosphooxy-L-glutamyl-tRNAGln;
(1c) 5-phosphooxy-L-glutamyl-tRNAGln + NH3 = L-glutaminyl-tRNAGln + phosphate

R03905
Reaction

ATP [CPD:C00002];
L-glutamyl-tRNA(Gln) [CPD:C06112];
L-glutamine [CPD:C00064];
H2O [CPD:C00001];
5-phosphooxy-L-glutamyl-tRNAGln;
NH3 [CPD:C00014]

In systems lacking discernible glutamine---tRNA ligase (EC 6.1.1.18), glutaminyl-tRNAGln is formed by a two-enzyme system. In the first step, a nondiscriminating ligase (EC 6.1.1.24, glutamate---tRNAGln ligase) mischarges tRNAGln with glutamate, forming glutamyl-tRNAGln. The glutamyl-tRNAGln is not used in protein synthesis until the present enzyme converts it into glutaminyl-tRNAGln (glutamyl-tRNAGlu 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. Some bacterial GatCAB complexes also has the activity of EC 6.3.5.6 [asparaginyl-tRNA synthase (glutamine-hydrolysing)].

EC 6.3.5.7 created 2002, modified 2019