Studies on Human Prostatic Acid Phosphatase. V. Isolation and Characterization of a Prostatic Acid Phosphatase Isozyme

Acid phosphatase (orthophosphoric monoester phosphohydrolase, EC 3. 1. 3. 2) isozyme 4 (pI 6.1) has been isolated from human prostate tissue. The enzyme showed a single protein band when examined by polyacrylamide gel disc electrophoresis. The purification coefficient was approximate 3.2 and the recovery of enzyme activity was 0.1% from the supernatant fraction. The molecular weight of the enzyme obtained by gel filtration was 100000, whereas that obtained by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate was 79000. The enzyme was not cross-reactive with acid phosphatase isozyme (pI 5.3) in immunodiffusion. Isozyme 4 had almost the same enzymic properties (Km, Ki, and optimum pH) as isozyme 2, but the specific activity of isozyme 4 was one-fourth of that of the latter.