Granzyme B (GZMB) is a serine protease stored in granules of activated cytotoxic T cells and NK cells. Upon target cell contact, granzyme B is directionally exocytosed and enters the target cell, assisted by perforin. With its unique substrate specificity (granzyme B cleaves after Asp), granzyme B processes and activates various pro-caspases thereby inducing apoptosis in the target cell. MW: 33 kDa. Purity ≥90%