Fundamental biochemical and immunological aspects of prostatic acid phosphatase

Prostatic acid phosphatase (PAP) was purified from human malignant prostate tissue by means of ammonium sulfate fractionation followed by sequential chromatographies of ion exchange, affinity column, and gel filtration. PAP has a molecular weight of 100,000 and consists of two subunits of 50,000. Owing, in part, to sialic acid contents in the molecule, PAP has multiple isoelectric points (pIs) at 4.2-5.5. In 0.2 M citrate, PAP has the highest affinity (Km 9.2 x 10(-5) M) in hydrolyzing alpha-naphthyl phosphate among the phosphomonoesters. Tartrate and heat at 37 degrees C for 2 hours almost completely inhibit PAP enzymic activity. By immunoprecipitate technique, anti-PAP heteroantiserum exhibited a distinct immunologic characteristics. Further, PAP possessed different antibody-binding site from enzyme hydrolytic site.