Dependence of 14WM9 catalytic activity on the chemical structure of the phosphorylated substrate. (A) Structures of the evaluated substrates. Note that for these experiments the hexapeptide was connected via an N-terminal Cys, rather than an N-terminal Ala as in Fig. 2. (B) Single-turnover assays, under conditions of Fig. 2 (Zn2+/Mn2+/Mg2+). kobs values from PAGE assays, top to bottom as listed in each plot: upper plot 0.54, 0.93, and 0.75 min–1; first four data sets in lower plot 0.39, 0.087, 0.11, and 0.13 h–1 (i.e., 6.5 × 10−3, 1.5 × 10−3, 1.8 × 10−3, and 2.2 × 10−3 min–1).