APG5 is required for autophagy. It conjugates to ATG12 and associates with isolation membrane to form autophagosomes. The conjugate detaches from the membrane immediately before or after autophagosome formation is completed. Conjugation to ATG12 is essential for autophagy, but is not required for association with isolation membrane. APG5 also plays an important role in the apoptotic process. Its expression is a relatively late event in the apoptotic process, occurring downstream of caspase activity.