Figure 6. Primary deuterium kinetic isotope effects on Kvβ2-catalyzed aldehyde reduction.

Initial velocity plots of the reaction at different concentrations of 4-nitrobenzaldehyde (A; 4-NB) and 4-nitroacetophenone (B; 4-NAP) with 0.15 mM NADPH or NADPD as indicated are shown. For each measurement, the Kvβ2 protein was mixed either with NADPH or NADPD (0.15 mM) and the reaction was initiated by the addition of the substrate. Time-dependent changes in total sample absorbance (multiple turnover mode) were measured. The values of initial velocity are normalized to the concentration of the total Kvβ2 protein in the cuvette. Data are shown as discrete points and curves are best fits of eq. [5] to the data (R²=0.99 for 4-NB and 0.97 for 4-NAP).