In Vitro Assays for Measuring Protein Histidine Phosphatase Activity

In order to obtain a detailed kinetic characterization, identify inhibitors, and elucidate the biological roles of an enzyme, it is advantageous to have a facile, sensitive enzyme assay protocol. Here we present a brief overview of the techniques available to monitor histidine phosphatase activity and provide protocols for measuring the activity and inhibition of PHPT1 in vitro using the fluorescent probe 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP). This assay uses small quantities of commercially available materials, making its use feasible for most laboratories.