Determinations of the inhibitory activity on monophenolase and diphenolase.

(I) The inhibitory effects on monophenolase activity of mushroom tyrosinase. (II) The inhibitory effects on steady-state activity of monophenolase. A, B and C represents the compound Y1, Y2 and Y3 respectively. (D) The inhibitory effects on diphenolase activity of mushroom tyrosinase.