Purity ~95% (SDS-PAGE). Prostate Specific Antigen (PSA, Kallikrein-3, Kallikrein III, Seminin, Semenogelase, g-Seminoprotein, P-30 antigen) is a chymotrypsin-like serine protease (kallikrein family) produced by the prostate epithelium and abundant in seminal fluid. PSA can be detected in the sera of patients with prostatic carcinoma. It is predominantly complexed to a liver-derived serine protease inhibitor, alpha-1-antichymotrypsin (ACT). A higher proportion of serum PSA is complexed to ACT in prostate cancer than in benign prostate hyperplasia. Source: Prostate Specific Antigen, from Human seminal fluid. Activity: >1mg/mg protein (ELISA)