Fig 2. Monophenolase activity.

A. Representation of i_M (degree of inhibition of the monophenolase activity) vs. the concentration of α-arbutin. The experimental conditions were [E]₀ = 80 nM, [L-tyrosine]₀ = 0.25 mM and [L-dopa]₀ = 0.01 mM. Inset. Spectrophotometric recordings of the effect of different concentrations of α-arbutin on the monophenolase activity of tyrosinase, using L-tyrosine as substrate. The experimental conditions were [E]₀ = 80 nM, [L-tyrosine]₀ = 0.25 mM, [L-dopa]₀ = 0.01 mM and α-arbutin (mM): a) 0, b) 1.5, c) 3, d) 6.5, e) 13, f) 20, g) 32 and h) 41. B. Representation of i_M (degree of inhibition of the monophenolase activity) vs. the concentration of β-arbutin. The experimental conditions were [E]₀ = 80 nM, [L-tyrosine]₀ = 0.25 mM and [L-dopa]₀ = 0.01 mM. Inset. Spectrophotometric recordings of the effect of different concentrations of β-arbutin on the monophenolase activity of tyrosinase, using L-tyrosine as substrate. The experimental conditions were [E]₀ = 80 nM, [L-tyrosine]₀ = 0.25 mM, [L-dopa]₀ = 0.01 mM and β-arbutin (mM): a) 0, b) 0.5, c) 1, d) 2, e) 5, f) 10 and g) 20.