Is an ortholog of human ATG4A (autophagy related 4A cysteine peptidase) and ATG4B (autophagy related 4B cysteine peptidase). Exhibits cysteine-type endopeptidase activity. Is involved in autophagy and proteolysis. Localizes to the cytoplasm. Is expressed in the embryonic cell\; the excretory cell\; the head muscle\; the somatic nervous system\; and the vulval precursor cell.