Granzymes are a family of serine proteases expressed by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells and are key components of immune responses to pathogens and transformed cells. In activated CTLs, granzyme A and granzyme B are processed and activated by cathepsin C, and they then function to induce apoptosis by two distinct pathways. Granzyme B proteolytically cleaves and activates members of the caspase family of cysteine proteases, including caspase-3, caspase-6, caspase-7 and caspase-9.
