Cysteine protease required for autophagy (PubMed:22767594, PubMed:30880001). Cleaves the C-terminal amino acid of ATG8 family proteins lgg-1, to reveal a C-terminal glycine (PubMed:22767594). Exposure of the glycine at the C-terminus is essential for ATG8 proteins conjugation to phosphatidylethanolamine (PE) and insertion to membranes, which is necessary for autophagy (Probable). Its cleavage activity is functionally redundant to atg-4.2, but it cleaves lgg-1 precursors more efficiently than atg-4.2 (Probable). Acts redundantly with atg-4.2 to promote the lgg-1 delipidation to release the protein from membranes, which facilitates multiple events during macroautophagy (PubMed:22767594). Unlike atg-4.2 does not seem to be required for autophagosome maturation (PubMed:30880001). [protein]-C-terminal L-amino acid-glycyl-phosphatidylethanolamide + H2O = [protein]-C-terminal L-amino acid-glycine + a 1,2-diacyl-sn-glycero-3-phosphoethanolamine Ubiquitously expressed in embryos. Belongs to the peptidase C54 family.