contain the residues essential for substrate recognition and catalytic
activity. They are activated either by proximity-induced
auto-proteolysis by interacting with a platform of adaptor proteins
through a protein interaction motif in the prodomain (DED, death
effector domain; or CARD, caspase recruitment domain), or by
cleavage by upstream proteases in a proteolytic cascade. These
proteolytic activities lead to separation of the p20 and p10 subunits
and separation of the prodomain of the p20 subunit, leading
to the formation of an antiparallel p20/p10/p10/p20 enzymatically
active heterotetramer [43]. In the following sections we describe
how caspase activity can be investigated by the use of fluorogenic
substrates, or by immunoblotting.