Alanine--tRNA ligase

UniProtKB accession:  P00957

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UniProtKB description:  Catalyzes the attachment of L-alanine to tRNA(Ala) in a two-step reaction: L-alanine is first activated by ATP to form Ala-AMP and then transferred to the acceptor end of tRNA(Ala). AlaRS also incorrectly activates the sterically smaller amino acid glycine as well as the sterically larger amino acid L-serine; generates 2-fold more mischarged Gly than Ser (PubMed:28362257). These mischarged amino acids occur because the of inherent physicochemical limitations on discrimination between closely related amino acids (Ala, Gly and Ser) in the charging step.