Hydrolysis of phosphate esters in aqueous solution promoted by cobalt(III)-tetraamine metallohydrolases: Chromatographic and spectroscopic studies

A combination of chromatographic and spectroscopic (Q-ToF/MS; FTIR) studies were conducted to further understand hydrolytic processes in reactions of phosphate mono- and phosphodiesters with model Cobalt(III)-tetraamine metallohydrolases of the type [CoL(OH)(OH2)](2+); L=(en)(2), (tn)(2); en=1,2-diaminoethane, tn=1,3-diaminopropane.High resolution mass spectroscopic (HRMS) analysis of the reaction fragments indicates that the monoester substrates undergo initial coordination to the metal center followed by an intramolecular hydroxyl attack on phosphorus, a process that is concerted with liberation of the bound alcoholic leaving group. The Co-III(tn)(2) complex displays twice as more reactivity towards both mono- and phosphodiesters compared to the (en)(2) analog under similar conditions, a behavior that is discussed in terms of the structural differences in the coordinated amine ligands. Plausible mechanisms for Co(III)-promoted hydrolysis of both the mono- and phosphodiesters are proposed.