Proteinase inhibitor 9 （PI-9，also designated cytoplasmic antiproteinase 3，or CAP3） is a 42 kDa member of the ovalbumin family of serpins that is expressed in placenta，lung and cytotoxic lymphocytes. PI-9 is a potent inhibitor of granzyme B and of granzyme B-mediated apoptosis，and is also an inhibitor of capase-1 and，to a smaller extent，caspase-4 and caspase-8. PI-9 expression is also upregulated in response to inflammatory stimuli. This upregulation protects cells from apoptosis induced by endogenously expressed or released granzyme B，particulary during target cell killling.
应用类型
Western blotting （2-4 ug/ml） and Immunohistochemistry （20 ug/ml）. It recognizes 42 kDa native human PI-9 and the 63 kDa PI-9 complexed to granzyme B. Reactivity to other species has not been tested.
