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Any of a family of protease enzymes that are central to initiating and carrying out programmed cell death (see apoptosis). They are formed, in response to certain triggers, from inactive precursors present in the cell. Proapoptotic signals include the activation of death receptors on the cell surface and bursting of mitochondria due to cell damage. Initiator caspases activate other caspases in a sequential cascade, culminating in effector caspases, such as caspases 3 and 6. Effector caspases cleave crucial cellular components, such as cytoskeletal proteins, and also activate DNase enzymes and inhibit DNA repair enzymes, leading to breakdown of the cell's DNA. Granzyme B, delivered into cells by cytotoxic T cells, can activate effector caspases directly. Release of cytochrome c from damaged mitochondria activates caspases 9 and 3, a process mediated by the formation of a multiprotein complex called an apoptosome.

Subjects: Chemistry — Biological Sciences.

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