Suicidal tendencies: Apoptotic cell death by caspase family proteinases

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