caspases

Apoptosis: "Caspases (cysteinyl aspartate-specific proteases) are enzymes that cleave specific proteins at aspartate residues. They contain cysteine residues in their active sites. Many caspase isoforms promote apoptosis. They can be activated by two main pathways: the death receptor pathway and the mitochondrial pathway.

At least 14 caspase isoforms have now been identified. These isoforms are broadly categorised into initiators, effectors and inflammatory caspases. Initiator caspases such as caspase-8 and 9 cleave and activate effector caspases such as caspase-3. Effector caspases cleave specific proteins that ultimately leads to cell death by apoptosis. Caspase activity leads to a proteolytic cascade in which one caspase can activate other caspases. This amplifies the apoptotic signalling pathway.

Cleavage of proteins by caspases can either activate them (e.g. other caspases and ICAD), or they can deactivate them (e.g. PKB/Akt, Raf-1 and PARP-1). Generally, proteins that promote apoptosis are activated, and proteins that promote survival are inactivated." MORE