Caspase是一類對天冬氨酸特異的半胱氨酸蛋白酶，是與秀麗隱桿線蟲Ced一3具有序列和結構同源性的一個蛋白家族，在細胞凋亡執行過程中直接參與早期凋亡啟動、信號傳遞及晚期凋亡效應，除此之外，部分caspase在細胞分化、細胞增殖、細胞移動中也發揮著作用。

Apoptosis, programmed Cell death, is triggered by a variety of stimuli, including cell surface receptors like FAS, mitochondrial response to stress, and cytotoxic T cells. Caspases are a class of cysteine proteases that includes several representatives involved in apoptosis. The caspases convey the apoptotic signal in a proteolytic cascade, with caspases cleaving and activating other caspases that then degrade other cellular targets that lead to cell death. The caspases at the upper end of the cascade include caspase-8 and caspase-9. Caspase-8 is the initial caspase involved in response to receptors with a death domain like FAS. The mitochondrial stress pathway begins with the release of cytochrome c from mitochondria, which then interacts with Apaf-1, causing self-cleavage and activation of caspase-9. Caspase-3, -6 and-7 are downstream caspases that are activated by the upstream proteases and act themselves to cleave cellular targets. Granzyme B and perforin proteins released by cytotoxic T cells induce apoptosis in target cells, forming transmembrane pores, and triggering apoptosis, perhaps through cleavage of caspases, although caspase-independent mechanisms of Granzyme B mediated apoptosis have been suggested.