Figure 3. Dopachrome formation by TYRtr under TYRP1tr protection.

Panel A: Representative time curves of the diphenol oxidase activities of TYRtr alone (black dots) and in the presence of TYRP1tr in 1:1 (purple dots) and 1:20 (cyan dots) ratios at pH 7.2 and 5.5 and at temperatures of 37°C and 43°C. Panel B: The initial velocity (V₀), the initial linear rate of dopachrome formation, defined as the number of nmoles of dopachrome formed per minute, was calculated from the slope of the progress curve for a reaction (top left). Maximum of dopachrome concentration presented in μM using the Beer-Lambert law, A=εbc, where A is absorbance; ε is the extinction coefficient for dopachrome at 475 nm (3700 M⁻¹ cm⁻¹); b is the path length of the well in which the sample is contained (cm); and c is the concentration of TYRtr in μM (top right). The time when the maximum dopachrome was formed is shown in minutes (bottom left). The melanin-like precipitation time is shown in minutes (bottom right). Values for TYRtr are shown as black bars, TYRtr in the presence of TRP1tr in a 1:1 ratio as purple bars, and TYRtr in the presence of TRP1tr in a 1:20 ratio as cyan bars. Errors represent the standard deviations from 3 independent experiments. Panel C: Pictures show melanin-like precipitation, which appeared during the incubation of L-DOPA with TYRtr and TYRtr/TYRP1tr mixtures in both 1:1 and 1:20 ratios at pH 7.2 and 5.5 and at temperatures of 37 and 43°C.