C Elution profiles of the POGLUT1 reaction products on reverse phase HPLC. hFIX-EGF repeat was incubated with wild-type or D233E mutant POGLUT1 and donor substrate, UDP-Glc or UDP-xylose (UDP-Xyl), at 37ºC overnight. Values on top of the peaks indicate the measured masses. Addition of Glc (162 Da) or xylose (132 Da) to hFIX-EGF (5696.2 Da) by wild-type POGLUT1 caused a shift to an earlier retention time (left). Similarly, the products exhibited a similar shift after incubation with POGLUT1D233E (right). These results indicate that POGLUT1D233E can add a single glucose or xylose to hFIX-EGF repeats and thus has residual enzymatic activity. 