Granzyme B is a serine protease mostly secreted by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. It is one of the major mediators of caspase-dependent apoptosis. Recent studies showed that Granzyme B can also be secreted by various non-cytotoxic cells and involved in degradation of extracellular matrix proteins thereby inducing inflammation and impairing wound healing. Thus, if intracellular activity of Granzyme B is mainly related to apoptosis, its extracellular activity has been linked to roles in arthritis, vascular pathologies, and other diseases. The SensoLyte^® 520 Granzyme B Assay Kit provides a convenient assay for screening of enzyme inhibitors or for continuous assay of Granzyme B activity using a novel internally quenched 5-FAM/QXL^®FRET substrate. Upon cleavage by Granzyme B, the FRET substrate will be separated into two fragments resulting in release of 5-FAM fluorescence which can be monitored at excitation /emission= 490 nm/520 nm. The kit can be used to detect the activity of Granzyme B enzyme in biological samples and purified enzyme preparations. This assay can detect as low as 0.1 ng/mL active granzyme B.The kit contains:

• QXL^® 520/ 5-FAM-based FRET peptide substrate (Ex/Em=490/520 nm upon cleavage)
• Assay buffer
• Recombinant Human Granzyme B
• Inhibitor
• Fluorescence reference standard for calibration
• A detailed protocol