Granzyme B, a 247 amino acid polypeptide, contains a leader sequence, which is cleaved by a signal peptidase and a two amino acid prodomain, which is cleaved by the lysosomal cysteine protease DPPI. The recombinant granzyme B is expressed in Pichia pastoris as the mature form and appears on SDS-PAGE as a triplet (~34, 32, and 30 kDa) due to three different glycosylations.
Cytotoxic granules secreted by natural killer (NK) cells and cytotoxic T Lymphocytes cells are part of the mechanism used for protecting the organism from virus infected and tumor cells. Granzyme B, a serine protease, is the most prominent granzyme in a family of 11 found in the cytotoxic granules. The granzymes enter the target cell with the assistance of perforin, a critical molecule of the cytotoxic granules. In the target cell, the granzymes act on specific substrates involved with the cell death via apoptosis.Granzyme B is a neutral serine protease that cleaves aspartic acid residues, inducing cell death by various pathways. It can cleave and activate most of the caspases in vitro and in vivo resulting in a massive amplification of the caspase dependent apoptotic pathway. In addition, granzyme B cleaves directly downstream caspase substrates as PARP DNA-PK2 and DFF45/ICAD leading to cell death. This pathway bypasses inhibition of apoptosis by viral caspase inhibitors found in virus infected cells. It has been shown that granzyme B is capable of inducing cytochrome C release from the mitochondria in a caspase independent way.
