EC - Aspartate—tRNAAsn ligase

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IntEnz Enzyme Nomenclature


Accepted name:
aspartate—tRNAAsn ligase
Other name:
nondiscriminating aspartyl-tRNA synthetase
Systematic name:
L-aspartate:tRNAAsx ligase (AMP-forming)



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 aspariginyl-tRNAAsn.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0050560
CAS Registry Number: 9027-32-1
UniProtKB/Swiss-Prot: (437) [show] [UniProt]


  1. Ibba, M. and Söll, D.
    Aminoacyl-tRNA synthesis.
    Annu. Rev. Biochem. 69: 617-650 (2000). [PMID: 10966471]
  2. Schmitt, E., Moulinier, L., Fujiwara, S., Imanaka, T., Thierry, J.C. and Moras, D.
    Crystal structure of aspartyl-tRNA synthetase from Pyrococcus kodakaraensis KOD: archaeon specificity and catalytic mechanism of adenylate formation.
    EMBO J. 17: 5227-5237 (1998). [PMID: 9724658]
  3. Becker, H.D. and Kern, D.
    Thermus thermophilus: a link in evolution of the tRNA-dependent amino acid amidation pathways.
    Proc. Natl. Acad. Sci. USA 95: 12832-12837 (1998). [PMID: 9789000]

[EC created 2002]