Enables Atg12 transferase activity and Atg8 ligase activity. Involved in autophagosome assembly; mitochondrial fragmentation involved in apoptotic process; and regulation of cilium assembly. Acts upstream of or within macroautophagy and negative regulation of phagocytosis. Predicted to be located in cytoplasm. Predicted to be part of cytoplasmic ubiquitin ligase complex. Predicted to be active in cytosol. Is expressed in several structures, including alimentary system; brain; cardiovascular system; genitourinary system; and immune system. Orthologous to human ATG3 (autophagy related 3). [provided by Alliance of Genome Resources, Apr 2022]