FIGURE 3.

Reduction of FAD in YUC6 by NADPH. A, titration of YUC6 (28 μm) with NADPH under anaerobic conditions. Reduction of YUC6 leads to a decrease of absorbance at 450 nm. The NADPH concentrations for the four spectra are 0, 7, 20, and 28.5 μm. B, reaction after mixing in the stopped-flow instrument equal volumes of NADPH (62 μm) with YUC6 (13 μm), as shown by difference spectra generated by subtracting the first spectrum at 0.00474 s from each successive spectrum. C, kinetics of YUC6 reduction monitored at 450 nm. The final concentrations of NADPH were 31 μm (solid line) and 93 μm (dotted line). YUC6 was 6.5 μm.