What is the role of caspases in apoptosis?

Caspases assist in initiating and carrying out the process of apoptosis. These enzymes are inactive zymogens and aspartate-specific cysteine proteases. Caspases go through a cascade of catalytic activation during the initiation of apoptosis. Activated caspases become inhibited by the inhibitor-of-apoptosis (IAP) group of proteins. Their activation is tightly regulated by a phylogenetically conserved death process which is crucial for the development and homeostasis of higher-level organisms. Caspases are essentially the executioners of apoptosis.

Caspases involved in apoptosis are categorized into two groups, initiator caspases and effector caspases. The initiator caspase is composed of an extended N-terminal prodomain of more than 90 amino acids while an effector caspase has 20-30 residues in its prodmain sequence. The activation of an effector caspase is carried out by  an initiator caspase through cleavage to separate the large and small subunits. An initiator caspase is automatically activated under apoptotic conditions. For example, the apoptosome is responsible for activating caspase-9.