FIG. 2.

Spectral changes observed upon dehydrogenation of benz[a]anthracene 1,2-dihydrodiol (A) and benzo[a]pyrene dihydrodiol (B) catalyzed by PDDH. The reactions were carried out under argon in a closed cuvette containing a suboptimal concentration of NAD⁺ in 1.0 ml of reaction mixture, pH 7.0. This allowed absorbance recording down to 260 nm. In panel A, the concentrations of NAD⁺ and benz[a]anthracene 1,2-dihydrodiol were 0.25 mM and 40 μM, respectively. The reaction was started at time zero by injecting 14 nM PDDH. In panel B, the cuvette contained 0.1 mM NAD⁺ and 8 μM benzo[a]pyrene dihydrodiol. The reaction was initiated at time zero by 35 nM PDDH. Spectra were recorded at the times indicated (seconds) after enzyme addition. The initial and final spectra are shown as thicker lines.