阿魏酸异辛酯抑制酪氨酸酶活性的动力学研究

Inhibitory Kinetics of 2-Ethylhexy Ferulate on Tyrosinase-catalyzing Reaction

在30℃,pH=6.8的Na2HPO4-NaH2PO4缓冲体系中,采用酶动力学方法研究阿魏酸异辛酯对酪氨酸酶单酚酶和二酚酶活力的抑制动力学。实验结果表明,阿魏酸异辛酯对酪氨酸酶单酚酶和二酚酶活性均有良好抑制作用,对单酚酶和二酚酶活力的相对抑制率达到50%的阿魏酸异辛酯浓度(IC50)约分别为0.24 mmol/L和0.45 mmol/L,比熊果苷抑制二酚酶活性的IC50值5.3 mmol/L小得多。阿魏酸异辛酯能明显延长单酚酶的迟滞时间,0.4 mmol/L阿魏酸异辛酯能使迟滞时间由1.1 min延长至3.6 min。Lineweaver-Burk图显示阿魏酸异辛酯对二酚酶的抑制作用表现为竞争性抑制,抑制常数(K)I为0.20 mmol/L。

The inhibitory kinetics of 2-ethylhexy ferulate on the activity of monophenolase and diphenolase contained in tyrosinase was studied by enzymological kinetic method with Na2HPO4-NaH2P04 buffer solution （pH=6.8） at 30 ~C. 2-ethylhexy ferulate was found to inhibit the monophenolase and diphenolase activity of tyrosinase well. The 2-ethylhexy ferulate concentrations leading to 50 % inhibitory rate （IC5o） were 0.24 mmol/L for monophenolase and 0.45 mmol/L for diphenolase, much less than that of arbutin （ICso =5.3 mmol/L for diphenolase activity）. 2-ethylhexy ferulate can extend the lag time of tyrosinase for oxidation of L-tyrosine, 0.4 mmol/L of 2-ethylhexy ferulate resulted in the extension of lag time from 1.1 rain to 3.6 min. The inhibition kinetics of 2-ethylhexy ferulate analyzed by Lineweaver-Burk plots demonstrated a competitive inhibitor for the oxidation of L-DOPA, the inhibition constant for inhibitor binding with enzyme, KI was determined to be 0.20 mmol/L.