摘要
报道了苯甲酸对蘑菇酪氨酸酶的单酚酶和二酚酶活力的影响以及抑制作用机理.研究结果表明,苯甲酸对蘑菇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1.20和1.00mmol/L.苯甲酸对蘑菇酪氨酸酶的单酚酶的迟滞时间有明显的延长效应,4mmol/L苯甲酸使得单酚酶的迟滞时间从42s延长到200s.测定苯甲酸对二酚酶的抑制作用表现为非竞争性抑制类型,测定抑制常数为0.95mmol/L.苯甲酸与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.作者提出抑制剂与酶分子的作用模型.
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. Benzoic acid was found to inhibit the monophenolase and odiphenolase activity of mushroom tyrosinase. The inhibition kinetics and mechanism of the enzyme were studied, and the results show that the inhibition of tyrosinase by benzoic acid is a reversible reaction with remaining enzyme activity. The inhibitor concentrations leading to 50% (IC50) activity lost were estimated to be 1.20 mmol/L for monophenolase activity and 1.00 mmol/L for diphenolase, respectively. Benzoic acid can extend the lag time of mushroom tyrosinase for oxidation of Ltyrosine. 40 mmol/L of benzoic acid resulted in the lag time extension from 42 s to 200 s. The inhibition kinetics analyzed by LineweaverBurk plots found benzoic acid to be a noncompetitive inhibitor for the oxidation of LDOPA, and the inhibition constant was determined to be 0.95 mmol/L. The combining of benzoic acid with the enzyme molecule resulted in decreasing of the quantal rate of the enzyme intrinsic fluorescence without apparent positionshifted.
出处
《厦门大学学报（自然科学版）》
CAS
CSCD
北大核心
2003年第1期102-106,共5页
Journal of Xiamen University：Natural Science
基金
福建省自然科学基金(B0110002)
教育部留学回国人员科研启动基金资助项目
关键词
蘑菇
酪氨酸酶
单酚酶活性
二酚酶活性
苯甲酸
抑制机理
果蔬保鲜
mushroom tyrosinase
monophenolase activity
o-diphenolase activity
benzoic acid
inhibitory mechanism
