Granzyme B is a member of the granzyme family of the serine proteases found specifically in the cytotoxic granules of cytotoxic T?lymphocytes (CTL) and natural killer (NK) cells. Granzyme B plays an essential role in granule-mediated apoptosis and may have additional roles in rheumatoid arthritis and in bacterial and viral infections. It activates various caspases and cleaves proteins such as aggrecan. The activity of recombinant pig Granzyme B was measured by its ability to cleaves a thioester substrate Z-Lys-SBzl?HCl. The reaction was performed in 0.05 M Tris, 0.15 M NaCl, 0.01% Triton X-100, pH 8.0 (Assay Buffer), initiated by addition 50 μL of various concentrations of GZMB (diluted by Assay Buffer) to 50 μL of 1.2 mM Substrate and DTNB mixture. The final well serves as a negative control with no GZMB, replaced with 50 μL assay buffer. Incubated at 25℃ for 5min, then read at a wavelength of 405 nm. The specific activity of recombinant pig Granzyme B is >440 pmol/min/μg.