Mouse ICAD Synthetic Peptide. ICAD is the inhibitor of caspase-3-activated DNase which is a substrate that controls nuclear apoptosis. ICAD has two isoforms: a functional isoform of 45kDa, ICAD-L/DNA fragmentation factor (DFF) 45; and a 35kDa isoform, ICAD-S/DFF35. Although both ICAD-L and ICAD-S can bind and inhibit CAD, only ICAD-L was reported to be functional. ICAD is cleaved to be inactivated and allow caspase-activated DNase (CAD) to execute nuclear internucleosomal apoptotic DNA fragmentation. In non-apoptotic cells, CAD is complexed with its inhibitor, ICAD. The activation of the CAD/ICAD complex occurs through the caspase 3-mediated cleavage of ICAD at residues 117 and 224, which results in three ICAD fragments that are then releas