Tyrosinase (EC 1.14.18.1) catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones which form brown or black pigments. Here, the inhibitory effects of 4-vinylbenzaldehyde and 4-vinylbenzoic acid on the activity of mushroom tyrosinase have been investigated. The results showed that both 4-vinylbenzaldehyde and 4-vinylbenzoic acid could inhibit both monophenolase activity and diphenolase activity of the enzyme. For the monophenolase activity, 4-vinylbenzoic acid could lengthen the lag time, but 4-vinylbenzaldehyde could not. Both 4-vinylbenzaldehyde and 4-vinylbenzoic acid decreased the steady-state activity, and the IC50 values were estimated as 93 microM and 3.0 mM for monophenolase activity, respectively. For the diphenolase activity, the inhibitory capacity of 4-vinylbenzaldehyde was stronger than that of 4-vinylbenzoic acid, and the IC50 values were estimated as 23 microM and 0.33 mM, respectively. Kinetic analyses showed that inhibition by both compounds was reversible and their mechanisms were mixed-II type; their inhibition constants were also determined and compared.

中文翻译：

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4-乙烯基苯甲醛和4-乙烯基苯甲酸对蘑菇酪氨酸酶活性的抑制作用。

酪氨酸酶（EC 1.14.18.1）既催化酪氨酸的羟基化为邻二酚，又催化邻二酚氧化为邻醌，形成棕色或黑色颜料。在这里，研究了4-乙烯基苯甲醛和4-乙烯基苯甲酸对蘑菇酪氨酸酶活性的抑制作用。结果表明，4-乙烯基苯甲醛和4-乙烯基苯甲酸均可抑制该酶的单酚酶活性和双酚酶活性。对于单酚酶活性，4-乙烯基苯甲酸可以延长滞后时间，而4-乙烯基苯甲醛则不能。4-乙烯基苯甲醛和4-乙烯基苯甲酸均会降低稳态活性，单酚酶活性的IC50值分别估计为93 microM和3.0 mM。对于双酚酶活性，4-乙烯基苯甲醛的抑制能力强于4-乙烯基苯甲酸，IC50值分别估计为23 microM和0.33 mM。动力学分析表明，这两种化合物的抑制作用都是可逆的，其机理为混合Ⅱ型。还确定并比较了它们的抑制常数。