Verification of α-KG consumption over the course of the WbpB reaction, indicating it is the required oxidant for NAD+ recycling. The reaction contained 0.75 mM UDP-GlcNAcA, 50 mM HEPES (pH 8.0), 2 mM α-KG and 2.5 g WbpB. Aliquots were removed from the reaction at selected time points, quenched, labeled with OPD, and analyzed by absorbance at 340 nm. Data represent the average of three experiments.