Interleukin-1 β converting enzyme (EC 3.4.22.36) (ICE) [1,2] is responsible for the cleavage of the IL-1 β precursor at an Asp-Ala bond to generate the mature biologically active cytokine. ICE a thiol protease composed of two subunits of 10 (p10) and 20 Kd (p20), both derived by the autocleavage of a 45 Kd precursor (p45). Two residues are implicated in the catalytic mechanism: a cysteine and an histidine. They are located in the P20 subunit after cleavage of the precursor. ICE belongs to a family of peptidases [3] which is implicated in programmed cell death (apoptosis) and which has been termed 'caspase' for cysteine aspase. ICE is known as Caspase-1 and the other members of this family [4] are:

• Caspase-2 (ICH-1, NEDD-2).
• Caspase-3 (also known as apopain, CPP32, Yama), a protease which, at the onset of apoptosis, proteolytically cleaves poly(ADP-ribose) polymerase (see <PDOC00360>) at an Asp-Gly bond.
• Caspase-4 (ICH-2, TX, ICErel-II).
• Caspase-5 (ICH-3, TY, ICErel-III).
• Caspase-6 (MCH-2).
• Caspase-7 (MCH-3, ICE-LAP3, CMH-1, SCA-2, LICE2).
• Caspase-8 (MCH-5, MACH, FLICE).
• Caspase-9 (MCH-6, ICE-LAP6).
• Caspase-10 (MCH-4, FLICE2).
• Caspase-11.
• Caspase-12.
• Caspase-13 (ERICE).
• Caspase-14.
• Caenorhabditis elegans ced-3 involved in the initiation of apoptosis.
• Drosophila Ice.

We have developed signature patterns for both active site residues. We also developed two profiles, one specific for the caspase P10 subunit and one for the caspase P20 subunit.