Atg3(Autophagy related 3) also known as APG3 is a ubiquitin-like-conjugating enzyme and is a component of ubiquitination-like systems involved in autophagy, the process of degradation, turnover and recycling of cytoplasmic constituents in eukaryotic cells. Atg3 plays a crucial role in the autophagy process by catalyzing the formation of the Atg8-phosphatidylethanolamine (Atg8-PE) conjugate, which is essential for the degradation of cellular components and organelles. The enzymatic activity of Atg3 is initiated by the removal of the C-terminal arginine residue of Atg8 by Atg4, a cysteine protease, which exposes a glycine residue that is subsequently activated by Atg7. The activated glycine is then transferred to Atg3, where conjugation to phosphatidylethanolamine (PE) occurs. Atg3 is predominantly expressed in tissues such as the kidney, placenta, liver, heart, and skeletal muscle, highlighting its importance in various physiological processes.