Glutaminyl-tRNA synthase (glutamine-hydrolysing) explained

Glutaminyl-tRNA synthase (glutamine-hydrolyzing)
Ec Number:	6.3.5.7
Cas Number:	52232-48-1
Go Code:	0050567

Glu-tRNA^Gln amidotransferase or glutaminyl-tRNA synthase (glutamine-hydrolysing) enzyme is an amidotransferase that catalyzes the conversion of the non-cognate amino acid glutamyl-tRNA^Gln to the cognate glutaminyl-tRNA^Gln..^[1] It catalyzes the reaction:

ATP + glutamyl-tRNA^Gln + L-glutamine

\rightleftharpoons ADP + phosphate + glutaminyl-tRNA^Gln + L-glutamate

This enzyme belongs to the family of ligases, specifically those forming carbon-nitrogen bonds carbon-nitrogen ligases with glutamine as amido-N-donor. The systematic name of this enzyme class is glutamyl-tRNA^Gln:L-glutamine amido-ligase (ADP-forming). This enzyme participates in glutamate metabolism and alanine and aspartate metabolism.

Function and evolutionary significance

Most bacterial and all archaea genomes do not encode a glutaminyl-tRNA synthetase (GlnRS). Instead they first synthesize the attachment of an amino acid on the tRNA^Gln by first attaching a non-cognate glutamate to the tRNA. Then these organisms use the amidotransferase: glutaminyl-tRNA synthase (glutamine-hydrolysing) enzyme to convert the glutamate attached to tRNA^Gln to glutamine.

Notes and References

1. Sheppard K, Yuan J, Hohn MJ, Jester B, Devine KM, Söll D . From one amino acid to another: tRNA-dependent amino acid biosynthesis . Nucleic Acids Research . 36 . 6 . 1813–1825 . April 2008 . 18252769 . 2330236 . 10.1093/nar/gkn015 .