The caspase family of cysteine proteases play a key role in apoptosis. Like other caspases in the family, caspase-4 is also synthesized as inactive pro-enzyme that is processed in cells by self-proteolysis and/or cleavage by another upstream protease. The processed form of caspase-4 consists of large and small subunits which associate to form an active enzyme. Caspase-4 has been implicated involving in Fas-mediated apoptosis.