中文摘要：

研究桑黄素（Morin）对蘑菇酪氨酸酶单酚酶和二酚酶活力的影响和抑制效应的结果表明：桑黄素对蘑菇酪氨酸酶的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％的抑制剂浓度（IC50）分别为0.08和1.02mmol／L；桑黄素对蘑菇酪氨酸酶的单酚酶的迟滞时间有明显的延长效应，0．175mmol／L桑黄素使得单酚酶的迟滞时间从24s延长到362s。迟滞时间增加了14倍，酶的稳态活力下降了61．9％；桑黄素对二酚酶的抑制作用表现为竞争性可逆抑制作用。抑制常数为0．55mmol／L．

英文摘要：

Tyrosinase （1.14.18.1） is a metalloenzyme oxidase which catalyzes two distinct reactions of melanin synthesis., the hydroxylation of a monophenol and the oxidation of o-diphenol to the corresponding o-quinone. In this paper,we find that Morin has potent inhibitory effects on the monophenolase and o-diphenolase activity of mushroom tyrosinase. The inhibition kinetics and mechanism of this compound on the enzyme were further studied. The results showed that the inhibition of Morin was a reversible reaction with remaining enzyme activity. The inhibitor concentrations leading to 50% （IC50） activity lost were estimated to be 0. 08 mmol/L for monophenolase activity and 1.02 mmol/L for diphenolase, respectively. Morin can extend the lag time of mushroom tyrosinase for oxidation of L-tyrosine,and it led to extending the lag time from 24 s to 362 s when its concentration was at 0. 175 mmoL/L. The inhibition kinetics analyzed by Lineweaver-Burk plots showed that Morin was a competitive inhibitor to the enzyme for the oxidation of LDOPA,and the inhibition constant was determined to be 0.55 mmol/L.