E1-like activating enzyme involved in the 2 ubiquitin-like systems required for cytoplasm to vacuole transport (Cvt) and autophagy. Activates atg12 for its conjugation with apg-4/atg5 and apg-6/atg8 for its conjugation with phosphatidylethanolamine. Both systems are needed for the apg-6/atg8 association to Cvt vesicles and autophagosomes membranes. Autophagy is essential for maintenance of amino acid levels and protein synthesis under nitrogen starvation. Required for selective autophagic degradation of the nucleus (nucleophagy) as well as for mitophagy which contributes to regulate mitochondrial quantity and quality by eliminating the mitochondria to a basal level to fulfill cellular energy requirements and preventing excess ROS production. Plays a role in the regulation of filamentous growth and chronological longevity (By similarity). Homodimer. The GxGxxG motif is important for the function, possibly through binding with ATP. Belongs to the ATG7 family.