Alkaline Phosphatase Activity Assay

Protein phosphatase, an enzyme that controls the removal of phosphate (PO₄ ^3-) group from protein molecules, regulates many fundamental cellular processes such as cell attachment, proliferation, differentiation and apoptosis. Pluripotent stem cells typically have higher levels of alkaline phosphatase activity than differentiated cell types (although osteoblasts retain this activity). Alkaline phosphatase staining/activity is often used as a biomarker of stem cells. Alkaline Phosphatase Assay (ALP) is optimized to detect phosphatase activity in biological samples using pNPP (4-nitrophenyl phosphate) as a colorimetric substrate. A water-soluble yellow product with a strong absorption at 405 nm is developed during the reaction of pNPP with phosphatase and can be detected with a microplate reader.