The Inhibitory Effect of Tyrosinase by Arbutin as Cosmetic Additive

Tyrosinase (1.14.18.1) is a metalloenzyme oxidase which catalyzes two distinct reactions of melanin synthesisthe hydroxylation of a monophenol and the oxidation of odiphenol to the corresponding oquinone. Arbutin was found to be able to inhibit the monophenolase and odiphenolase activity of tyrosinase. In the present work, The inhibition kinetics and mechanism of the enzyme were farther studied. The results show that the inhibition of tyrosinase by arbutin is a reversible reaction with remaining enzyme activity. The inhibitor concentrations leading to 50% (IC50) activity lost were estimated to be 5.32 mmol/L for diphenolase. Arbutin can extend the lag time of the enzyme for oxidation of Ltyrosine. 160 mmol/L of arbutin resulted in the lag time extension from 82 s to 430 s. The inhibition kinetics analyzed by LineweaverBurk plots showed that arbutin was a competitive inhibitor for the oxidation of LDOPA, and the inhibition constants were determined to be 2.98 mmol/L for the free enzyme.The writing mechanism of arbutin as cosmetic additive was discussed.