GATC (glutamyl-tRNA amidotransferase subunit C) is a mitochondrial enzyme that catalyzes the formation of correctly charged glutaminyl-tRNA through transamidation of misacylated glutamyl-tRNA(Gln) in the presence of glutamine and ATP. This process generates an activated gamma-phospho-Glu-tRNA(Gln) intermediate and is essential for accurate mitochondrial protein synthesis. GATC functions as part of the glutamyl-tRNA(Gln) amidotransferase complex and facilitates proper tRNA charging, a critical step in translational fidelity. Genetic defects in GATC cause Combined Oxidative Phosphorylation Deficiency 42 (COXPD42), a severe mitochondrial disorder. The disease association reflects the critical dependence of mitochondrial respiration on accurate protein synthesis, as impaired tRNA aminoacylation leads to defective synthesis of electron transport chain components and oxidative phosphorylation machinery. While specific clinical manifestations of GATC mutations have not been detailed in available literature, the disease classification suggests severe metabolic consequences affecting cellular energy production. GATC represents an important quality-control mechanism in mitochondrial translation, and its dysfunction exemplifies how disrupted aminoacyl-tRNA synthesis impairs bioenergetic capacity and causes multisystem mitochondrial disease.