In enzymology, a glutamine-tRNA ligase (EC 18.104.22.168) is an enzyme that catalyzes the chemical reaction
- ATP + L-glutamine + tRNAGln AMP + diphosphate + L-glutaminyl-tRNAGln
The 3 substrates of this enzyme are ATP, L-glutamine, and tRNA(Gln), whereas its 3 products are AMP, diphosphate, and L-glutaminyl-tRNA(Gln).
This enzyme belongs to the family of ligases, to be specific those forming carbon-oxygen bonds in aminoacyl-tRNA and related compounds. The systematic name of this enzyme class is L-glutamine:tRNAGln ligase (AMP-forming). Other names in common use include glutaminyl-tRNA synthetase, glutaminyl-transfer RNA synthetase, glutaminyl-transfer ribonucleate synthetase, glutamine-tRNA synthetase, glutamine translase, glutamate-tRNA ligase, glutaminyl ribonucleic acid, and GlnRS. This enzyme participates in glutamate metabolism and aminoacyl-trna biosynthesis.
Structural studies 
As of late 2007, 15 structures have been solved for this class of enzymes, with PDB accession codes 1EUQ, 1EUY, 1EXD, 1GSG, 1GTR, 1GTS, 1NYL, 1O0B, 1O0C, 1QRS, 1QRT, 1QRU, 1QTQ, 1ZJW, and 2HZ7.
- Ravel JM, Wang S, Heinemeyer C and Shive W (1965). "Glutamyl and glutaminyl ribonucleic acid synthetases of Escherichia coli W. Separation, properties, and stimulation of adenosine triphosphate-pyrophosphate exchange by acceptor ribonucleic acid". J. Biol. Chem. 240: 432–438. PMID 14253448.