Although MUP is widely used for detecting phosphatases in solution it is not well suited for living cell or continuous assays since MU (4-methylumbelliferone), the enzymatic product, which only develops maximum fluorescence at pH value of >10. Thus it is also difficult to use MUP for the detection of phosphatases that have acidic optimal pH range such as acid phosphatases. AAT Bioquest is pleased to offer CF-MUP Plus that is developed to address this pH limitation associated with MUP substrates. CF-MU exhibits maximum fluorescence above pH 5.0, thus CF-MUP substrate can be well used for continuous phosphatase assays. It can also be used for the assays that require acidic pH such as acid phosphatases and some protein phosphatases.