FIGURE 11.

Two possible reaction mechanisms of the dephosphorylation of undecaprenyl pyrophosphate in UppP. A, based on the present model, the Upp dephosphorylation reaction is likely to begin with histidine (His-30) initiating a nucleophilic attacking on the phosphorus center to form a phosphohistidine intermediate. The negative charges of the phosphate groups are chelated by a magnesium ion to facilitate the transferring of the phosphate group to the histidine. Then a water (or OH⁻ ion) makes a second nucleophilic attack on the phosphate of the phosphohistidine intermediate. B, histidine initiates a nucleophilic attack on a water molecule, which acts as a second nucleophilic attack on the phosphate of the Upp substrate.