Caspases in apoptotic death.

Caspases are the central mediators of normal and pathological apoptotic death. They are cysteine proteases that cleave after aspartic acid. The inactive pro-enzymes are proteolytically processed and activated through mechanisms of recruitment to signalling complexes, upstream activator caspases or autoactivation. Many amplifying cascades exist in caspase activation pathways that are evolutionarily conserved. The human caspase family contains at least 10 members which form 3 groups based on substrate specificity, proteolytic targets and functional actions. The crystal structure has been solved for members from two of these groups with inhibitory peptides bound in the active site. These structures have allowed tremendous insight into mechanisms of catalysis, substrate binding and substrate specificity. Enlightened knowledge of enzyme-substrate interactions has led to the design of many inhibitors that are active in animal models of caspase-mediated cell death. Testing in animal models should lead to drugs for therapeutic intervention in the many human diseases characterised by excessive apoptotic cell death.