Caspases are a crucial element in the process of apoptosis. They are a type of enzyme called proteases and have a cysteine molecule in the active site. Their target proteins are specific aspartic acids. Caspases are made within the cell as an inactive form, procaspases. Activation occurs by proteolytic cleavage at one or two aspartic acids and catalysed by alrady active caspases. Once activated an amplifying proteolytic cascade is formed as the caspases cleave, thus activating, other procaspases.
The leakage of Cytochrome C from the mitochondial intermembrane space initiates the activation of the first caspases. In apoptosis, there are two forms of caspase that are used; initiator caspases and executioner caspases. It is the initiator procaspases that are first activated, and then go onto cleave and activate the executioner procaspases.
The activated caspases progress apoptosis by cleaving nuclear lamins, which leads to nuclear fragmentation. DNase is activated and fragements the cell DNA and DNase inhibitor is cleaved. The cell detaches from it's neighbours through caspases cleaving the cytoskeleton. This leads to loss of communication with the extracellular matix.
Certain caspases are also used to mediate inflammation.