19-F NMR studies of the binding of a fluorine-labeled phosphonate ion to E. coli alkaline phosphatase.

The interaction of a fluorinated phosphonate with Zn-2+-and Mn-2+-alkaline phosphatase as studied by 19-F NMR revealed a stoichiometry of 1:1 for the binding of the phosphonate anion to the enzyme. In the presence of two metal ions, one fluorinated phosphonate ion was found to interact strongly with the enzyme, while a different interaction was observed when the number of metal ions per enzyme exceeded two. Phosphate replaced enzyme bound phosphonate, as is shown by the 19-F NMR spectra. No direct interaction between the fluorinated phosphonate and the metal ion responsible for enzyme activity was indicated by the 19-F NMR data. This observation supports the idea of a considerable distance between metal ion and substrate binding site in Escherichia coli alkaline phosphatase.