Caspase-9, also known as APAF-3, Mch6 and ICE-LAP6, is a 35-37 kDa member of the peptidase C14A family of enzymes. Caspase-9 is an initiator caspase that is part of the intrinsic apoptosis pathway. It is widely expressed and is particularly important during development. Following mitochondrial disruption, Cytochrome c is released from mitochrondria and interacts with APAF-1, resulting in Pro-Caspase-9 dimerization. The act of dimerization activates Pro-Caspase-9, leading to its autocleavage into p35 and p12 subunits or to its activation of Caspase-3. Activated Caspase-3 can also act on Pro-Caspase-9, generating a 37 kDa subunit and a 10 kDa subunit.