Acid phosphatases (AP) dephosphorylate phosphate groups from phosphate esters under acid conditions. Different acid phosphatase isozymes are found in different organs, and their serum levels are used as a diagnostic for disease in the corresponding organs. Elevated prostatic acid phosphatase levels may indicate the presence of prostate cancer and elevated tartrate-resistant acid phosphatase levels may indicate the bone disease. BioVision’s Acid Phosphatase Assay Kit is a high sensitivity, simple, direct and HTS-ready colorimetric assay designed to measure AP activity in serum and other samples. It is suitable for research and drug discovery. The kit uses p-nitrophenyl phosphate (pNPP) as a phosphatase substrate which turns yellow (λmax = 405 nm) when dephosphorylated by AP. The kit can detect µU acid phosphatase activity in samples.