Caspase-9 is a member of the peptidase family C14 that contains a CARD domain. This caspase is active as a heterotetramer and has been reported to have two isoforms. Pro-Caspase-9 has been reported to be approximately 47 kD. This caspase is present in the cytosol and, upon activation, translocates to the mitochondria. Caspase-9 is involved in the caspase activation cascade responsible for apoptosis execution and cleaves/activates Caspase-3 and Caspase-6. Caspase-9 is inhibited by the dominant negative isoform, Bcl-XL, c-IAP1, c-IAP2, XIAP, and Livin. This caspase becomes activated when recruited to Apaf-1/cytochrome c complex, and following cleavage by Apaf-1, granzyme B, Caspase-3, possibly Caspase-8 and Caspase-10 into large p37 and small p10 subunits. Caspase-9 interacts with BIRC7 and has been shown to cleave PARP and vimentin. The Poly6342 antibody has been shown to be useful for western blotting ofhuman Human, Mouse and rat caspase-9 (p10) and caspase-9 precursor.