In enzymology, a cysteine–tRNA ligase () is an enzyme that catalyzes the chemical reaction:
ATP + -cysteine + tRNA AMP + diphosphate + -cysteinyl-tRNA
The three substrates of this enzyme are ATP, -cysteine, and tRNA, whereas its three products are AMP, diphosphate, and -cysteinyl-tRNA.
There are two isozymes in humans, encoded by the genes CARS1 (cytoplasmic) and CARS2 (mitochondrial). This enzyme belongs to the family of ligases, specifically those forming carbon–oxygen bonds in aminoacyl-tRNA and related compounds. The systematic name of this enzyme class is -cysteine:tRNA ligase (AMP-forming). Other names in common use include cysteinyl-tRNA synthetase, cysteinyl-transferRNA synthetase, cysteinyl-transfer ribonucleate synthetase, and cysteine translase. This enzyme participates in cysteine metabolism and aminoacyl-tRNA biosynthesis.
Structural studies
As of late 2007, three structures have been solved for this class of enzymes, with PDB accession codes , , and .
References