Figure 4. LctD-his₆ catalyzes oxidation of L-lactate, but not D-lactate, to pyruvate.

HPLC chromatogram of LctD-his₆ in vitro enzyme reactions with (A) L-lactate as the substrate at time 0, (B) L-lactate as the substrate after 15 min, and (C) D-lactate as the substrate after 15 min. Pyruvate and D- and L-lactate were detected using a refractive index detector, and data are displayed as peak height (microvolts). Using commercially available standards, it was determined that pyruvate is detected at approximately 11.6 to 12.1 min and lactate (D and L) is detected at approximately 14.6 to 15.2 min. Representative data are shown for experiments that were performed in duplicate or triplicate.