4-Methylumbelliferyl phosphate (4-MUP) is a fluorogenic substrate of alkaline phosphatases^[1]. In Vitro: 4-Methylumbelliferyl phosphate monoester previously described as one of a series of 4-methylumbelliferone conjugates is later found to be the PlP2-pyrophosphate diester and is not hydrolysed by serum phosphomonoesterases . 4-Methylumbelliferyl phosphate has a significant advantage over currently available substrates in that its useful concentration range extends to about 0.1 μM^[1].
If the concentration of 4-Methylumbelliferyl phosphate is held constant and the pH is varied, the activity of the enzyme passes through a maximum^[1].