Figure 4.

Determination of the modes of action of (Z)-BPTT analogs. Lineweaver–Burk plots for the inhibition of mushroom tyrosinase by (Z)-BPTT analogs 1–3 (A–C) and 6 (D). Modes of action were determined by analyzing Lineweaver–Burk plots. Data are mean 1/V values; defined as the inverse of increased dopachrome absorbance per min at a wavelength of 492 nm as determined by three independent experiments using six different concentrations of l-DOPA as substrate. The concentrations of the (Z)-BPTT analogs used were 0 µM (filled circles), 1 µM (unfilled circles), 2 µM (filled triangles), and 4 µM (unfilled triangles) for analogs 1 and 6; 0 µM (filled circles), 2.5 µM (unfilled circles), 5 µM (filled triangles), and 10 µM (unfilled triangles) for analog 2; and 0 µM (filled circles), 0.4 µM (unfilled circles), 0.8 µM (filled triangles), and 1.6 µM (unfilled triangles) for analog 3. The modified Michaelis–Menten equation was used: 1/V_max = (1/K_M)(1 + [S]/K_i), where V_max, K_M, [S], and K_i represent maximum reaction rate, the Michaelis–Menten constant, L-DOPA concentration, and the inhibition constant, respectively. All experiments were performed independently 3 times.