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, PDB, 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]