Prostatic Acid Phosphatase (PAP) belongs to the histidine acid phosphatase family. PAP can catalyze the hydrolysis of member of phosphate monoestyers, including phosphorylated protein. PAP can high expression in metastasized prostate cancer, moderately expression level in bone diseases, blood cell disease, and the concentration of PAP is used to monitor and assess the proession of prostate cancer. The optimum PH of PAP is from 4 to 6; its activity can be inhibited by L(+)-tartrate.