甘醇酸对蘑菇酪氨酸酶的抑制作用

The Inhibition of Mushroom Tyrosinase by Glycolate

在蘑菇酪氨酸酶抑制剂的筛选实验中,发现甘醇酸对蘑菇酪氨酸酶有明显的抑制作用,可以导致酪氨酸酶的单酚酶活力和二酚酶活力下降,实验结果表明,甘醇酸抑制蘑菇酪氨酸酶的单酚酶和二酚酶活力下降50%的抑制剂浓度(IC50)分别为29.74和1.80 mmol/L.对单酚酶活力的迟滞时间也有明显的延迟效应,30 mmol/L的甘醇酸可以使迟滞时间延长了250%.甘醇酸对二酚酶的抑制作用是可逆过程,抑制类型为混合型.通过动力学分析,测得甘醇酸对游离酶(E)和酶-底物络合物(ES)的抑制常数分别为0.72和5.05 mmol/L,通过研究甘醇酸对酪氨酸酶的抑制作用机理,为进一步研究设计新型酪氨酸酶抑制剂奠定基础.

Tyrosinase（EC 1.14. 18. 1）, a key enzyme for melanin-biosynthesis, is widely distributed in nature. It contains both monophenolase activity and diphenolase activity. In this paper, it is reported that glycolate can inhibit activity of mushroom tyrosinase, and glycolate evidently affects the lag time of the monophenolase. With the increase of concentration of glycolate, the lag time of the enzyme for oxidation of L-tyrosine greatly extended and the steady-state rate of monophenolase decreased. The inhibitory concentration leading to 50 % activity lost（IC50 ） was estimated to be 29.74 mmol/L for monophenolase,and the concentration for diphenolsae was estimated to be 1.80 mmol/L. When the concentration reaches 30 mmol/L,the lag time is almost extended by 250 %. The inhibition kinetics and mechanism of the diphenolase activity of the enzyme by glycolate also have been studied. The results showed that glycolate was a reversible inhibitor of mushroom tyrosinase. Lineweaver-Burk plots indicated that glycolate was a mixed type inhibitor ,and its inhibition constants were KI = 0.721 mmol/L, KIS = 5. 049 mmol/L respectively. Together these results provide a basis for the design and development of new inhibitors in the future.