Involved in the activation cascade of caspases responsible for apoptosis execution (By similarity). Inhibited by the baculovirus anti-apoptotic protein p35. Cleaves p35 and nuclear immunophilin FKBP46. Heterotetramer that consists of two anti-parallel arranged heterodimers, each one formed by a 19/18 kDa (p19/18) and a 12 kDa (p12) subunit. The two subunits are derived from the precursor sequence by an autocatalytic mechanism. Belongs to the peptidase C14A family.