摘要
以曲酸为效应物,研究对酪氨酸酶的单酚酶和二酚酶活力的影响.结果表明,曲酸对酪氨酸酶的单酚酶和二酚酶活性均有抑制作用,其效应为可逆抑制效应.测定导致单酚酶活力和二酚酶活力下降50%的抑制剂浓度(IC50)分别为31.0和20.0μmol/L.曲酸对酪氨酸酶的单酚酶的迟滞时间有明显的延长效应,60μmol/L曲酸使得单酚酶的迟滞时间从52s延长到390s.曲酸对二酚酶的抑制作用表现为混合型抑制类型,抑制常数KI和KIS分别为13.0和100.0μmol/L.曲酸和酶的结合导致天然酶的内源荧光的量子产率下降,但荧光发射峰没有位移.通过曲酸对酪氨酸酶的抑制作用研究阐明曲酸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 synthesisthe hydroxylation of a monophenol and the oxidation of odiphenol to the corresponding oquinone. Kojic acid was found to inhibit the monophenolase and odiphenolase activity of mushroom tyrosinase. The inhibition kinetics and mechanism of the enzyme were further studied. The results show that the inhibition of tyrosinase by kojic acid is a reversible reaction with remaining enzyme activity. The inhibitor concentrations leading to 50% (IC50) activity lost were estimated to be 31 μmol/L for monophenolase activity and 20 μmol/L for diphenolase, respectively. Kojic acid can extend the lag time of the enzyme for oxidation of Ltyrosine. 60 μmol/L of kojic acid resulted in the lag time extension from 52 sec to 390 sec. The inhibition kinetics analyzed by LineweaverBurk plots showed kojic acid to be a mixed typed inhibitor for the oxidation of LDOPA,and the inhibition constants were determined to be 13.0 μmol/L for the free enzyme and 100.0 μmol/L for the enzymesubstrate complex. The combining of kojic acid with the enzyme molecule resulted in the decreasing of the quanta rate of the enzyme intrinsic fluorescence without appearance positionshifted.The whitening mechanism of kojic acid as cosmetic additive was discussed.
出处
《厦门大学学报（自然科学版）》
CAS
CSCD
北大核心
2003年第5期652-656,共5页
Journal of Xiamen University：Natural Science
基金
教育部留学回国人员科研启动基金
福建省自然科学基金(B0110002)资助
