Chapter 1 Isolation and assay of caspases

Publisher Summary This chapter provides an overview on the structure, organization and the mechanism of activation of caspases, with focus particularly on the assay of caspase-9. The human caspase family consists of 11 members and divided in three subfamilies is based on phylogenetic analysis. Caspases, synthesized as inactive zymogens, with molecular sizes ranging from 30 to 55 kDa are based on functional analysis of caspases, and are broadly classified in three groups—namely, cytokine activators, upstream apoptosis initiator caspases, and downstream apoptosis executioner caspases. Caspases exist as latent zymogens in normal cells with extremely low intrinsic protease activity. In caspases with short prodomains, there is no significant autoactivation observed in mammalian cells. These caspases are known as “downstream caspases” because they depend on active initiator caspases for their activation by proteolytic cleavage. Another mechanism of caspase activation is through aspartate-specific serine proteases.