The Enzyme Database

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Accepted name: aspartate—tRNAAsn ligase
Reaction: ATP + L-aspartate + tRNAAsx = AMP + diphosphate + L-aspartyl-tRNAAsx
Other name(s): nondiscriminating aspartyl-tRNA synthetase
Systematic name: L-aspartate:tRNAAsx ligase (AMP-forming)
Comments: 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.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9027-32-1
1.  Ibba, M. and Söll, D. Aminoacyl-tRNA synthesis. Annu. Rev. Biochem. 69 (2000) 617–650. [DOI] [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 (1998) 5227–5237. [DOI] [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 (1998) 12832–12837. [DOI] [PMID: 9789000]
[EC created 2002]

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