对醛基苯甲酸对蘑菇酪氨酸酶的抑制作用

The Inhibitory Effect on Mushroom Tyrosinase by p-Aldehydobenzoic Acid

酪氨酸酶是一种同时具有单酚酶和二酚酶活力的酶.对醛基苯甲酸(ABA)对蘑菇酪氨酸酶活力的影响研究结果表明:ABA只对蘑菇酪氨酸酶的二酚酶活性有抑制作用,而对单酚酶没抑制作用.ABA对二酚酶的抑制作用显示浓度关系,测定导致酶活力下降50%的抑制剂浓度(IC50)为0.98 mmol/L.ABA对二酚酶的效应为可逆的非竞争性的抑制,抑制常数KI为0.94 mmol/L.本文得到的结果与苯甲酸和苯甲醛的效应进行了比较.

Tyrosinase (1.14.18.1) is an enzyme that contains monophenolase activity and diphenolase activity.In this paper,p-aldehydobenzoic acid is discovered to inhibit the o-diphenolase activity,but not have any effects on monophenolase activity.The lag time of the enzyme for oxidation of L-tyrosine does not extended and the steady-state rate of monophenolase does not decrease with the increase of concentration of p-aldehydobenzoic acid.The inhibition kinetics and mechanism of the diphenolase activity of the enzyme by p-aldehydobenzoic acid have been studied.The results show that the inhibition of p-aldehydobenzoic acid on the diphenolase activity is a reversible reaction with remaining enzyme activity.The inhibitor′s concentration leading to 50% (IC_(50)) activity lost is estimated to be 0.98 mmol/L.The inhibition kinetics analyzed by Lineweaver-Burk plots shows that p-aldehydobenzoic acid is a non-competitive inhibitor for the oxidation of L-DOPA,and its inhibition constant is 0.94 mmol/L.Compared with benzoic acid and benzaldehyde,(p-aldehydobenzoic) acid has the potentiality to be as pesticide which can inhibit the enzyme activity of tyrosinase in some pest.