摘要
在30℃,pH=6.8的Na2HPO4-NaH2PO4缓冲体系中,采用酶动力学方法研究了肉桂酸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,肉桂酸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%的肉桂酸浓度(IC50)约分别为0.37mmol·L-1和0.61mmol·L-1,比熊果苷抑制二酚酶活性的IC50值5.3mmol·L-1小得多。肉桂酸能明显延长单酚酶的迟滞时间,0.4mmol·L-1肉桂酸能使迟滞时间由1.1min延长至2.3min。Lineweaver-Burk图显示肉桂酸对二酚酶的抑制作用表现为非竞争性抑制,表观米氏常数(Km)为0.68mmol·L-1,抑制常数(KI)为0.58mmol·L-1。
The inhibitory kinetics of cinnamic acid on the activity of monophenolase and diphenolase contained in tyrosinase was studied via enzymological kinetic method with Na2HPO4-NaH2PO4 as buffer solution (pH=6.8) and at 30℃. It was found that cinnamic acid can inhibit both the monophenolase and diphenolase activities of tyrosinase well. Moreover, cinnamic acid can also extent the lag time of catalytic oxidation of L-DOPA(L-3,4-dihydroxyphenylalanine) by monophenolase, for example, 0.4 mmol·L^-1 of cinnamic acid can extend the lag time from 1.1 min to 2.3 min. The cinnamic acid concentrations corresponding to 50% inhibitory rate (IC50) are 0.37 mmol·L^-1 for monophenolase and 0.61 mmol·L^-1 for diphenolase, respectively, and the latter is much less than that of arbutin (IC50=5.3 mmol·L^-1 for diphenolase ). The inhibition kinetics of cinnamic acid analyzed by Lineweaver-Burk plots demonstrate that the inhibition effect of cinnamic acid for the oxidation of L-DOPA expresses as what a noncompetitive inhibitor does. The apparent Michaelis constant Km and the inhibition constant of noncompetitive reversible inhibitor K1, were determined to be 0.68mmol·L^-1 and 0.58 mmol·L^-1, respectively.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2007年第2期345-349,共5页
Journal of Chemical Engineering of Chinese Universities
基金
广东省自然科学基金资助项目(011563
04020114)
关键词
酪氨酸酶
肉桂酸
抑制作用
动力学
单酚酶
二酚酶
tyrosinase
cinnamic acid
inhibitory effect
kinetics
monophenolase
diphenolase