The Supporting Information contains experimental methods for the hydrolysis reactions, phosphate transfer reactions and the wet-dry physicochemical cycle along with the associated 31 P NMR spectra and plots of changes in concentration/yield of phosphorylated species over time. The reaction schemes and rate equations used to determine the rate constants for the hydrolysis reactions are contained with the fitted plots and a Table of the calculated rate constants. in situ NMR characterisation data of the phosphorylated histidyl intermediate are included. (PDF)