Since the discovery of structural and functional similarities between the product of the nematode cell-death gene Ced-3 and mammalian interleukin-1β-converting enzyme（ICE）, an expanding family of cysteine proteases genes have been coloned and shown to play a key role in execution stage of mammalian cell apoptosis. Several substrates are found to be cleaved by the active ICE/CED-3 proteases（because of cysteine protease with aspartates specificity, also called caspase）,and subsequent cytological effect is induced.