Caspase 2 proteolytically cleaves other proteins. It belongs to a family of cysteine proteases called caspases that only cleave proteins at an amino acid following a aspartic acid residue. Within this family, caspase 2 is part of the Ich-1 subfamily. It is one of the most conserved caspases in different species of animal. Caspase 2 has a similar amino acid sequence to initiator caspases, including caspase 1, caspase 4, caspase 5 and caspase 9. It is produced as a zymogen, which contains a long pro-domain that is similar to that of caspase 9 and contains a protein interaction domain known as a CARD domain. Pro-caspase-2 contains two subunits, p19 and p12.In addition, caspase 2 may form a complex with the catalytic subunit of DNA-PK (DNA-PKcs) and PIDD (LRDD), which is involved in DNA repair after DNA damage.