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Background
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Trifluoroacetic acid salt of a peptide substrate labeled at the carboxy end with AFC (7-amino-4- trifluoromethyl coumarin). Designed to measure Caspase-4, Caspase-5, or Caspase-9 activity in vitro. Caspase-4 (also known as ICErel-II, TX, or ICH-2), Caspase-5 (also known as ICErel-III or TY), and Caspase-9 (also known as ICE-LAP6 or Mch6) are members of the caspase family of cysteine proteases involved in apoptosis. Caspases-4 and - 5 belong to Group I (along with caspase-1), which prefer the tetrapeptide substrate sequence WEHD and are thought to be involved in inflammation through the maturation of pro-IL-1betaa. Their role in apoptosis, however, is unclear. Caspase-9 is a member of Group III, which prefer the substrate sequence (L/V)jEXD. Since Caspase-9 has a strict requirement for His in the P4 position, it is not unexpected that the LEHD inhibitor sequence would work well on this caspase. The Group III caspases optimal recognition sequence resembles the activation sites within several effector caspase proenzymes, implicating the Group III enzymes as upstream components in the proteolytic cascade that amplifies the death signal.
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