Caspase Activation and Mechanism in Apoptosis

Caspases are enzymes that are involved in apoptosis.  They are naturally transcribed and translated in the cell, but their unmodified form includes a domain that keeps them inactive.  Once apoptosis is triggered, modifier proteins cleave this domain, allowing the caspases to tetramerize into functional units. A caspase cascade is initiated, in which caspases sequentially cleave the inhibitory domains of their downstream caspases.  In order to kill the cell, caspases work primarily by destroying membranes. They form pores in mitochondrial membranes, allowing Cytochrome c release. This dissipates the membrane potential, so the mitochondria are unable to produce energy for the cell.  Caspases can also perforate the cell membrane, allowing the osmotic pressure to run to equilibrium, which spells disaster for the cell.