香草酸对酪氨酸酶催化活性的抑制作用

The Inhibitory Effect of Vanillic Acid on Tyrosinase Activity

采用酶动力学方法研究了香草酸对酪氨酸酶单酚酶和二酚酶活力的抑制效应。结果表明,香草酸对酪氨酸酶单酚酶和二酚酶活性均有抑制作用,导致单酚酶活力和二酚酶活力下降50%的香草酸浓度(IC50)约分别为1.3 mmol/L和2.6 mmol/L。香草酸能明显延长单酚酶的迟滞时间,2 mmol/L香草酸能使迟滞时间由1.1 m in延长至4.7 m in。香草酸对二酚酶的抑制作用表现为混合型抑制,对游离酶的抑制常数(KI)和对酶-底物络合物的抑制常数(KIS)分别为1.76 mmol/L和8.57 mmol/L。

The inhibitory effects of vanillic acid on the activity of monophenolase and diphenolase contained in tyrosinase was studied using enzymological kinetic method. Vanillic acid was found to inhibit the monophenolase and diphenolase activity of tyrosinase. The vanillic acid concentration leading to 50% activity lost （IC50） were 1.3 mmol/L for monophenolase and 2.6 mmol/L for diphenolase. Vanillic acid can extend the lag time of tyrosinase for oxidation of L-tyrosine. Vanillic acid of 2 mmol/L resulted in the lag time extension from 1. 1 min to 4.7 min. The inhibition kinetics analyzed by Lineweaver-Burk plots found vanilic acid to be a mixed inhibitor for the oxidation of L-DOPA, and the equilibrium constants for inhibitor binding with free enzyme KI and with enzyme-substract complex KIS were 1.76 mmol/L and 8.57 mmol/L respectively.