Caspase-3 is a crucial cysteine protease involved in the execution phase of apoptosis. It is activated by cleavage at specific aspartic acid residues, leading to the formation of its active form, which then cleaves a variety of substrates, including poly (ADP-ribose) polymerase (PARP), contributing to DNA fragmentation and cell death. Caspase-3 is activated through various pathways, including the Fas/FasL and granzyme B pathways, and plays a central role in the apoptotic response to diverse cellular signals. Its activity is tightly regulated and is a key determinant in the progression of cell death.