AARS1 (alanyl-tRNA synthetase 1) is a dual-function enzyme with primary roles in protein synthesis and metabolic sensing. Canonically, AARS1 catalyzes aminoacylation of tRNA(Ala) through a two-step reaction: alanine activation by ATP to form Ala-AMP, followed by transfer to tRNA(Ala) 1. The enzyme also possesses editing activity to remove incorrectly charged tRNAs 1. Beyond translation, AARS1 functions as a critical lactate sensor and lactyltransferase 2. Under high lactate conditions, AARS1 catalyzes protein lactylation by activating lactate to form lactate-AMP and transferring the lactyl moiety to lysine residues in target proteins including p53, TEAD1, and YAP1 34. AARS1-mediated p53 lactylation impairs DNA binding and transcriptional activation, thereby inhibiting p53 activity and promoting tumorigenesis 4. In the Hippo pathway, AARS1 lactylation of YAP1 and TEAD1 activates the complex to promote cell proliferation 3. Recent studies reveal AARS1 lactylates histone H3K18 and STAT1 to regulate ferroptosis in diabetic nephropathy 5 and sepsis-induced acute lung injury 6. Mutations in AARS1 are associated with Charcot-Marie-Tooth disease and developmental epileptic encephalopathy, linking the enzyme to neurological disorders.