FIG. 5.
Inhibition of PDDH by 3,4-dihydroxyphenanthrene at a constant concentration of phenanthrene dihydrodiol. Enzyme assays were carried out in the absence (•) or in the presence of 3,4-dihydroxyphenanthrene at concentrations of 2.5 (▪), 5 (⧫), 10 (▴), or 20 (▾) μM. The dihydrodiol concentration was kept constant at 25 μM. Data were fitted by the Michaelis equation as described in the legend of Fig. 4. A plot of the calculated Km/Vmax ratios as a function of inhibitor concentration gave a straight line (not shown), and an inhibition constant of 10.9 μM was calculated.