Aspartate—tRNA(Asn) ligase

From Wikipedia, the free encyclopedia
  (Redirected from Aspartate-tRNAAsn ligase)
Jump to: navigation, search
Aspartate---tRNAAsn ligase
EC number
CAS number 9027-32-1
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum

Aspartate---tRNAAsn ligase (EC, nondiscriminating aspartyl-tRNA synthetase) is an enzyme with systematic name L-aspartate:tRNAAsx ligase (AMP-forming).[1][2][3] This enzyme catalyses the following chemical reaction

ATP + L-aspartate + tRNAAsx AMP + diphosphate + aspartyl-tRNAAsx

The 3 substrates of this enzyme are ATP, L-asparagine, and tRNAAsx, whereas its 3 products are AMP, diphosphate, and asparaginyl-tRNAAsx.

When this enzyme acts on tRNAAsp, it catalyses the same reaction as EC, aspartate---tRNA ligase. It has, however, diminished discrimination, so that it can also form aspartyl-tRNAAsn. This relaxation of specificity has been found to result from the absence of a loop in the tRNA that specifically recognizes the third position of the anticodon [1]. This accounts for the ability of this enzyme in, for example, Thermus thermophilus, to recognize both tRNAAsp (GUC anticodon) and tRNAAsn (GUU anticodon). The aspartyl-tRNAAsn is not used in protein synthesis until it is converted by EC, asparaginyl-tRNA synthase (glutamine-hydrolysing), into asparaginyl-tRNAAsn.

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-asparaginyl:tRNAAsx ligase (AMP-forming). This enzyme is also called nondiscriminating asparaginyl-tRNA synthetase. This enzyme participates in alanine and asparagine metabolism.


  1. ^ Ibba, M.; Söll, D. (2000). "Aminoacyl-tRNA synthesis". Annu. Rev. Biochem. 69: 617–650. doi:10.1146/annurev.biochem.69.1.617. PMID 10966471. 
  2. ^ Schmitt, E.; Moulinier, L.; Fujiwara, S.; Imanaka, T.; Thierry, J.C.; Moras, D. (1998). "Crystal structure of aspartyl-tRNA synthetase from Pyrococcus kodakaraensis KOD: archaeon specificity and catalytic mechanism of adenylate formation". EMBO J. 17: 5227–5237. doi:10.1093/emboj/17.17.5227. PMC 1170850Freely accessible. PMID 9724658. 
  3. ^ Becker, H.D.; Kern, D. (1998). "Thermus thermophilus: a link in evolution of the tRNA-dependent amino acid amidation pathways". Proc. Natl. Acad. Sci. USA. 95: 12832–12837. doi:10.1073/pnas.95.22.12832. PMC 23616Freely accessible. PMID 9789000.