Assaying Cdc25 Phosphatase Activity

To determine the activity of all human Cdc25 phosphatases, two different methods are described. For assaying phosphatase activities of recombinant Cdc25 proteins produced in Escherichia coli or insect cells, a fluorimetric assay using fluorescein diphosphate (FDP) as a substrate is recommended. To analyze endogenous Cdc25 phosphatase activities of immuno-precipitates from total cellular extracts, the physiological substrate Cdk1/cyclin B1 is most sensitive.