IUBMB Enzyme Nomenclature

EC 6.1.1.23

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 6.1.1.12, 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 6.3.5.6, asparaginyl-tRNA synthase (glutamine-hydrolysing), into asparaginyl-tRNAAsn.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 9027-32-1

References:

1. Ibba, M. and Söll, D. Aminoacyl-tRNA synthesis. Annu. Rev. Biochem. 69 (2000) 617-650. [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. [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. [PMID: 9789000]

[EC 6.1.1.23 created 2002]


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