Suicidal tendencies: Apoptotic cell death by caspase family proteinases

Certain proteases are not merely degradative enzymes but are highly regulated signaling molecules that control critical biological processes via specific limited proteolysis. Caspase proteinases and their central role in apoptotic cell death provide a prime example of this concept. These cysteine proteinases exist as latent zymogens; however, once activated by apoptotic signals, they systematically dismantle and package the cell by cleaving key cellular proteins solely after aspartate residues. Here we review caspase proteinases with an emphasis on their structure, activation, and critical role in the apoptotic mechanism.