熊果甙作为化妆品添加剂对酪氨酸酶抑制作用

The Inhibitory Effect of Tyrosinase by Arbutin as Cosmetic Additive

熊果甙(Arbutin)作为化妆品添加剂具有增白效果,主要是由于它对皮肤酪氨酸酶有抑制作用.本文研究了熊果甙对酪氨酸酶的单酚酶和二酚酶活力的抑制效应.结果表明,熊果甙对酪氨酸酶活性的抑制作用表现为可逆抑制效应.熊果甙对酪氨酸酶的单酚酶的效应主要表现于迟滞时间有明显的延长,但对稳态酶活力的影响不显著.160mmol/L熊果甙使得单酚酶的迟滞时间从82s延长到430s,增大4.24倍,稳态酶活力仅下降16%.熊果甙对二酚酶的抑制作用显示浓度关系,测定导致酶活力下降50%的抑制剂浓度(IC50)为5.30mmol/L,其抑制作用为竞争性类型,抑制常数KI为2.98mmol/L.本文通过研究熊果甙对酪氨酸酶的抑制作用机理,阐明了熊果甙作为化妆品添加剂的增白作用机理.

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.