Prostatic acid phosphatase (PAP), also prostatic specific acid phosphatase (PSAP), is an enzyme produced by the prostate. It may be found in increased amounts in men who have prostate cancer or other diseases. The highest levels of acid phosphatase are found in metastasized prostate cancer. . Description: Human seminal fluid. Alternative Names: PAP protein, PAP antigen, Prostatic Acid Phosphatase protein