Caspase-9 is a member of the caspase-family of cysteine proteases. Similar to other caspases, caspase-9 also exists in cells as an inactive proenzyme. During the initiation of apoptosis procaspase-9 is processed at aspartate residues to form active caspase-9. As one of the initiator caspases, active caspase-9 functions to trigger activation of downstream effector caspases, leading to disassembly of cell structures. The recombinant active human caspase-9 was expressed in E. coli. The active caspase-9 is routinely tested for its ability to enzymatically cleave these two substrates Ac-LEHD-pNA or Ac-LEHD-AFC.
