The activation of caspases has been shown to occur under a variety of conditions that induce apoptosis. These proteolytic enzymes cleave numerous protein substrates in response to a proapoptotic signal that results in the disassembly of the cell. Caspases are synthesized as precursors that undergo proteolytic maturation to form an active enzyme complex. We have used the CaspaTag Caspase Activity kit from Intergen (Purchase, NY) to detect these proteases in living cells during apoptosis. The assay is based on carboxyfluorescein-labeled fluoromethyl ketone (FMK) peptide inhibitors of caspases. The inhibitor irreversibly binds to active caspases to distinguish caspase-positive cells from caspase-negative cells by an increase in fluorescence intensity at 530 nm. The following protocol examines caspase activity in regards to AVD during apoptosis.
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