Phosphorus-31 NMR relaxation studies of diethyl P-methoxyphenyl phosphate bound to phosphotriesterase

The effect of Mn2+/Mn2+, Mn2+/Zn2+ and Mn2+/Cd2+ reconstituted phosphotriesterase on the 31P spin lattice (1/T1) relaxation rate of diethyl p-methoxyphenyl phosphate has been investigated. In the presence of Mn2+/Mn2+ phosphotriesterase, the spin lattice relaxation rate of the phosphorus atom is enhanced giving an upper limit for the phosphorus-metal root mean-sixth average distance of 4.2 Å. These results demonstrate for the first time that substrates for phosphotriesterase bind in close proximity to the binuclear metal center.