ATG4B (Autophagy-related protein 4B) is a member of the ATG4 family, which also includes ATG4A, ATG4C, and ATG4D. ATG4B is a cysteine protease with specific cleaving activity, responsible for processing and delipidating the covalent conjugation of Atg8/LC3 to phosphatidylethanolamine (PE), crucial for autophagy. ATG4B is primarily expressed in the cytoplasm and affects cell survival and metabolism by regulating autophagy. Specific gene expression and mutations can impact autophagic function, associated with the development of various diseases.