对氰基苯酚对蘑菇酪氨酸酶的抑制作用

报道了对氰基苯酚对蘑菇酪氨酸酶单酚酶和二酚酶活力的抑制效应.结果表明,对氰基苯酚对酪氨酸酶活性的抑制作用表现为可逆抑制作用,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,对稳态酶活力有显著抑制作用.0.50mmol/L对氰基苯酚使得单酚酶的迟滞时间从18s延长到80s,增大4.4倍,稳态酶活力下降80%.对氰基苯酚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0.80mmol/L,其抑制作用为竞争性类型,抑制常数KI为0.31mmol/L.通过研究对氰基苯酚对酪氨酸酶的抑制作用机理,试图寻找新型的有增白作用的化妆品添加剂.

The Inhibitory Effect on Mushroom Tyrosinase by 4-cyanophenol

Tyrosinase (1.14.18.1) is a copper-containing oxidase that catalyzes two distinct reactions of melanin synthesisthe hydroxylation of a monophenol and the oxidation of o-diphenol to the corresponding o-quinone. 4-Cyanophenol was found to inhibit the monophenolase and o-diphenolase activity of mushroom tyrosinase. 4-Cyanophenol inhibited the monophenolase activity. The lag time of the enzyme for oxidation of L-tyrosine extended and the steady-state rate of monophenolase decreased. When the concentration of 4-cyanophenol reached 0.50 mmol/L, the steady-state rate of the enzyme dropped by 80 % of the total activity, and the lag time extended from 18 sec to 80 sec. The inhibition kinetics and mechanism of the diphenolase activity of the enzyme by 4-cyanophenol were farther studied. The results show that the inhibition of 4-cyanophenol is a reversible reaction with remaining enzyme activity. The inhibitor concentrations leading to 50% (IC_(50)) activity lost were estimated to be 0.80 mmol/L for diphenolase. The inhibition kinetics analyzed by Lineweaver-Burk plots was showed that 4-cyanophenol is a competitive inhibitor for the oxidation of L-DOPA, and the inhibition constants were determined to be 0.31 mmol/L for the free enzyme. Comparing with arbutin, 4-cyanophenol is a stronger inhibitor for the diphenolase activity. In this paper, we discuss the writing mechanism of 4-cyanophenol as cosmetic additive.