Caspase 1/ICE (Interleukin-1b Converting Enzyme) is expressed as a proenzyme of 45kD in many tissues. Upon stimulus it gets activated by proteolytic cleavage. Active Caspase 1 is a tetramer of two subunits p10 and p20 in 2;2 proportion. Caspase 1 (cystein aspartic-specific protease 1) cleaves its substrates after an aspartate residue. It cleaves Interleukin b into its active form which further exerts its proinflammatory effects. Overexpression of caspase 1 can induce apoptosis in fibroblast which can be inhibited by overexpression of Crm A, a protein from pox virus.