FIG. 3.

pH optimum of T. forsythia NanH. Strain KCL117 [E. coli BL21(DE3)/pET30::nanH] was grown in LB until mid-exponential phase and for a further 18 h after induction with 1 mM IPTG. Cell lysates were prepared as described in Materials and Methods and assayed using 4-MU-NeuNAc in sodium citrate buffer (pH 3.0 to 6.0), sodium phosphate buffer (pH 6.0 to 8.0), potassium phosphate buffer (pH 6.5 to 7.5), and Tris-HCl (pH 7.5 to 8.9). The release of 4-MU was determined as fluorescence intensity (excitation and emission wavelengths of 380 and 460 nm, respectively). The data shown are the means from at least three independent experiments. Error bars represent ± the standard error of the mean.