Aspartate—tRNA(Asn) ligase
| Aspartate—tRNAAsn ligase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 6.1.1.23 | ||||||||
| CAS no. | 9027-32-1 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| |||||||||
Aspartate—tRNAAsn ligase (EC 6.1.1.23, 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 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.
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.
References
[edit]- ^ Ibba M, Soll D (2000). "Aminoacyl-tRNA synthesis". Annual Review of Biochemistry. 69: 617–50. doi:10.1146/annurev.biochem.69.1.617. PMID 10966471.
- ^ Schmitt E, Moulinier L, Fujiwara S, Imanaka T, Thierry JC, Moras D (September 1998). "Crystal structure of aspartyl-tRNA synthetase from Pyrococcus kodakaraensis KOD: archaeon specificity and catalytic mechanism of adenylate formation". The EMBO Journal. 17 (17): 5227–37. doi:10.1093/emboj/17.17.5227. PMC 1170850. PMID 9724658.
- ^ Becker HD, Kern D (October 1998). "Thermus thermophilus: a link in evolution of the tRNA-dependent amino acid amidation pathways". Proceedings of the National Academy of Sciences of the United States of America. 95 (22): 12832–7. Bibcode:1998PNAS...9512832B. doi:10.1073/pnas.95.22.12832. PMC 23616. PMID 9789000.
