Caspases are a family of protease enzymes that play essential roles in apoptosis. In the intrinsic pathway, initiator caspases such as caspase-9 are first activated, which then cleave and activate effector caspases like caspase-3. These effector caspases execute the apoptotic program by cleaving various cellular substrates, leading to the characteristic morphological changes of apoptosis, such as cell shrinkage, nuclear fragmentation, and DNA fragmentation.
