Involved in the activation cascade of caspases responsible for apoptosis execution. Might function by either activating some proteins required for cell death or inactivating proteins necessary for cell survival (PubMed:7958843). Associates with PIDD1 and CRADD to form the PIDDosome, a complex that activates CASP2 and triggers apoptosis in response to genotoxic stress (By similarity). Strict requirement for an Asp residue at P1, with 316-Asp being essential for proteolytic activity and has a preferred cleavage sequence of Val-Asp-Val-Ala-Asp-|-. Heterotetramer that consists of two anti-parallel arranged heterodimers, each one formed by a p18 subunit and a p12 subunit. Forms a complex named the PIDDosome with PIDD1 and CRADD. Interacts with NOL3 (via CARD domain); inhibits CASP2 activity in a phosphorylation-dependent manner. High level expression seen in the embryonic CNS, liver, lung, kidney, small intestine, and hair follicles of vibrissae. Moderate expression seen in the skin, oral mucosa, skeletal muscle, submandibular gland and thymus. In the adult, it is highly expressed in spleen, lung and kidney. Moderately in the brain, heart, testis, liver. Low levels in the thymus, skeletal muscle, ovary and gut. During embryonic development is highly expressed in several types of mouse tissue undergoing high rates of programmed cell death such as central nervous system and kidney. The CARD domain mediates a direct interaction with CRADD. The mature protease can process its own propeptide, but not that of other caspases. Belongs to the peptidase C14A family.