Aspartate-tRNA(Asn) Ligase

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Aspartate---tRNAAsn ligase (EC, nondiscriminating aspartyl-tRNA synthetase) is an enzyme with systematic name L-aspartate:tRNAAsx ligase (AMP-forming). This enzyme catalyses the following chemical reaction ATP + L-aspartate + tRNAAsx ⇌ {\displaystyle \rightleftharpoons } 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, 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. 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.
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Aspartate-tRNAAsn ligase
L-aspartate:tRNAAsx ligase (AMP-forming)
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