Si Yue-Xiu, Wang Zhi-Jiang, Park Daeui, Jeong Hyoung Oh, Ye Sen, Chung Hae Young, Yang Jun-Mo, Yin Shang-Jun, Qian Guo-Ying
College of Biological and Environmental Sciences, Zhejiang Wanli University, Ningbo, PR China.
Biosci Biotechnol Biochem. 2012;76(6):1091-7. doi: 10.1271/bbb.110910. Epub 2012 Jun 7.
We studied the inhibitory effects of isorhamnetin on mushroom tyrosinase by inhibition kinetics and computational simulation. Isorhamnetin reversibly inhibited tyrosinase in a mixed-type manner at Ki=0.235±0.013 mM. Measurements of intrinsic and 1-anilinonaphthalene-8-sulfonate(ANS)-binding fluorescence showed that isorhamnetin did not induce significant changes in the tertiary structure of tyrosinase. To gain insight into the inactivation process, the kinetics were computed via time-interval measurements and continuous substrate reactions. The results indicated that inactivation induced by isorhamnetin was a first-order reaction with biphasic processes. To gain further insight, we simulated docking between tyrosinase and isorhamnetin. Simulation was successful (binding energies for Dock6.3: -32.58 kcal/mol, for AutoDock4.2: -5.66 kcal/mol, and for Fred2.2: -48.86 kcal/mol), suggesting that isorhamnetin interacts with several residues, such as HIS244 and MET280. This strategy of predicting tyrosinase interaction in combination with kinetics based on a flavanone compound might prove useful in screening for potential natural tyrosinase inhibitors.
我们通过抑制动力学和计算模拟研究了异鼠李素对蘑菇酪氨酸酶的抑制作用。异鼠李素以混合型方式可逆地抑制酪氨酸酶，其抑制常数Ki = 0.235±0.013 mM。对酪氨酸酶的固有荧光和1-苯胺基萘-8-磺酸盐（ANS）结合荧光的测量表明，异鼠李素不会引起酪氨酸酶三级结构的显著变化。为深入了解失活过程，通过时间间隔测量和连续底物反应计算动力学。结果表明，异鼠李素诱导的失活是一个具有双相过程的一级反应。为进一步深入了解，我们模拟了酪氨酸酶与异鼠李素之间的对接。模拟成功（Dock6.3的结合能为-32.58 kcal/mol，AutoDock4.2的结合能为-5.66 kcal/mol，Fred2.2的结合能为-48.86 kcal/mol），表明异鼠李素与几个残基相互作用，如HIS244和MET280。这种结合基于黄酮类化合物的动力学来预测酪氨酸酶相互作用的策略，可能在筛选潜在的天然酪氨酸酶抑制剂方面很有用。
