Hydrolases;
Acting on peptide bonds (peptidases);
Cysteine endopeptidases
Reaction(IUBMB)
Strict requirement for an Asp residue at position P1 and with a marked preference for His at position P2. It has a preferred cleavage sequence of Leu-Gly-His-Asp!Xaa
Comment
Caspase-9 is an initiator caspase, as are caspase -2 (EC 3.4.22.55), caspase-8 (EC 3.4.22.61) and caspase-10 (EC 3.4.22.63) [1]. Caspase-9 contains a caspase-recruitment domain (CARD) in its N-terminal prodomain, which plays a role in procaspase activation [1]. An alternatively spliced version of caspase-9 also exists, caspase-9S, that inhibits apoptosis, similar to the situation found with caspase-2 [1]. Phosphorylation of caspase-9 from some species by Akt, a serine-threonine protein kinase, inhibits caspase activity in vitro and caspase activation in vivo [1]. The activity of caspase-9 is increased dramatically upon association with the apoptosome but the enzyme can be activated without proteolytic cleavage [2,3]. Procaspase-3 is the enzyme's physiological substrate [2]. Belongs in peptidase family C14.
