Disclosed is a kinase and phosphatase assay based on Fluorescence Resonance Energy Transfer (FRET). The assay involves; dephosphorylating a phosphorylated substrate molecule labelled with an energy acceptor of a FRET pair with a phosphatase; contacting the dephosphorylated substate molecule with an energy donor of the FRET pair and a binding partner that only binds phosphorylated substrate molecule and the detection molecule. The contacting of the substrate molecule with the detection molecule and the binding partner result in binding of the phosphorylated substrate molecule and the detection molecule to the binding partner. The assay also includes a step of determining phosphatase activity by measuring energy transfer from the energy donor of the phosphorylated substrate molecule bound to the binding partner to the energy acceptor of the detection molecule bound to the binding partners. The assay can be useful for screening for compounds that can modulate specific signalling pathways.
KINASE AND PHOSPHATASE ASSAY BASED ON FRET