Transesterification of phosphodiester by a zinc-containing cyclen derivative: Identification of the active species

The active site analogue 2 of alkaline phosphatase was synthesized and its hydrolytic activity was tested. Efficient hydrolysis was observed at pH > 8 at various concentrations of the hydrolytic species. The cyclic phosphate 3 derived from transesterification could be identified by ³¹P-NMR spectroscopy. A comparison of the hydrolysis results with the species distribution curve revealed the ZnL-OH species as the active complex. The complex stability constant (log K_ZnL) of ligand 7 was determined to be 13.7 (± 0.5). K′ for the hydrolysis of the p-nitrophenyl phosphate ester of propylene glycol (1) with 2 (0.02 M, pH = 8.35) is 1.5 × 10^-3 s^-1 at 50°C.