Figure 1.
Progress curves for the inhibition of monophenolase of mushroom tyrosinase by α-arbutin at 30°C.
The reaction media (3.0 mL) contained 0.5 mM L-tyrosine in 50 mM phosphate buffer (pH 6.8), the indicated concentration of α-arbutin, and mushroom tyrosinase (20 µg/mL). The concentrations of α-arbutin for curves 1∼4 were 0, 1.67, 3.34, 4.18 mmol·L−1. The reaction was started by the addition of the enzyme.
Figure 2.
Effects of α-arbutin on the enzyme activity and the lag time of monophenolase activity of mushroom tyrosinase.
Assay conditions: 3.0 ml 50 mM phosphate buffer pH 6.8, containing 0.5 mM L-tyrosine. The reaction was started by the addition of the enzyme (20 µg/mL).
Figure 3.
Activation rate of diphenolase of mushroom tyrosinase by α-arbutin.
Assay conditions: 3.0 ml 50 mM phosphate buffer pH 6.8, containing 0.5 mM L-Dopa, different concentrations of α-arbutin and mushroom tyrosinase (6.67 µg/mL).
Figure 4.
Progress curves for the activation of diphenolase of mushroom tyrosinase by α-arbutin
. The reaction media (3.0 mL) contained 0.5 mM L-Dopa in 50 mM phosphate buffer (pH 6.8), the indicated concentration of α-arbutin, and mushroom tyrosinase (6.67 µg/mL). The concentrations of α-arbutin for curves 1∼3 were 0, 5, 10 mmol·L−1.
Figure 5.
Lineweaver-Burk plots for activation of α-arbutin on mushroom tyrosinase for the catalysis of L-Dopa at 30°C, pH 6.8.
The reaction media (3.0 mL) contained 50 mM phosphate buffer (pH 6.8), different concentrations of L-Dopa assubstrate,different concentrations of α-arbutin and mushroom tyrosinase (6.67 µg/mL). Concentrations of α-arbutin for curves 1∼3 were 0, 5, 10 mmol·L−1, respectively.
Table 1.
Kinetic parametes of diphenolase by α-arbutin.
Figure 6.
The chemical structure of ascorbic acid.