Inhibitory Mechanism and Kinetics Study of Apple Polyphenols on the Activity of Tyrosinase

Tyrosinase is the key enzyme in the biosynthesis of melanin. In order to investigate the effect of apple polyphenols on tyrosinase activity, the enzyme kinetic method was used. The concentration of apple polyphenols, which caused the tyrosinase activity to be lost by 50%, was 1.0 mg ml(-1) for monophenolase and 0.9 mg ml(-1) for disphenolase. When the concentration of apple polyphenols was 2.0 mg ml(-1), the lag time before reaction of monophenolase was extended from 1.2 to 4.5 min. Inhibition kinetics analysis suggested that apple polyphenols were reversible and mixed inhibitors for tyrosinase with an inhibition equilibrium constant 2.3 mmol l(-1). The results indicated that apple polyphenols were ideal tyrosinase inhibitors and could be used in food and cosmetics.