阳离子双子表面活性剂诱导的α-CT超活性和构象变化（英文）  

Enzymatic Superactivity and Conformational Change of α-CT Induced by Cationic Gemini Surfactant

作　　者：白光月[1] 刘君玲[1] 王九霞[2] 王玉洁[2] 李艳娜[1] 赵扬[1] 姚美焕[1] 

机构地区：[1]河南师范大学化学化工学院,精细化学品绿色制造河南省协同创新中心,绿色化学介质与反应教育部重点实验室,河南新乡453007 [2]河南科技学院化学化工学院,河南新乡453003

出　　处：《物理化学学报》2017年第5期976-983,共8页Acta Physico-Chimica Sinica

基　　金：supported by the National Natural Science Foundation of China(21273061,21573061);Scientific Research Project of Higher Education of Henan Province,China(17A150032)~~

摘　　要：报道了α-糜蛋白酶(α-CT)催化活性及其与阳离子双子表面活性剂(N,N′-双(十二烷基二甲基)-1,2-二溴化癸二铵,简写为12-10-12)相互作用热力学的关系。酶活性通过紫外-可见吸收光谱法测量底物醋酸2-萘酯(2-NA)分解速率进行评估。在较短的培育时间内,12-10-12能够激活α-CT,得到催化2-NA分解的超活性,同时也加速了酶变性的动力学过程。在低于α-CT/12-10-12体系的临界聚集浓度(cac12-10-12,CT)时,显示一个钟形的大的超活性区。酶活性随时间变化的结果表明,由12-10-12激活的α-CT有高的酶活性和低的变性稳定性。进而采用等温滴定量热(ITC)、稳态荧光光谱和差示扫描量热(DSC)技术研究了12-10-12诱导α-CT超活性的机理。结果表明酶的超活性来源于正电荷的12-10-12与α-CT相互作用对α-CT内部结构的扰动,使得酶的构象变得比处于弱相互作用平衡的天然酶的构象更加松弛,这有利于2-NA水解酸性产物释放的动力学,而同时也导致了α-CT结构的不稳定性。This work presents the correlation of the enzymatic activity of α-chymotrypsin （a-CT） with the thermodynamics of interaction between α-CT and the cationic gemini surfactant decanediyl-α, α-bis （dodecyldimethylammonium bromide） （12-10-12）. The enzymatic activity was assessed by the rate of 2-naphthyl acetate （2-NA） hydrolysis obtained from UV-Vis absorption spectra. The superactivity of α-CT in the catalytic hydrolysis of 2-NA was obtained by activation with 12-10-12 in a short incubation time; the activated α-CT showed faster denaturation kinetics. The larger superactivities appeared in a bell shape below the critical aggregation concentration （cac12-10-12,CT） of the mixed gemini/α-CT systems in buffered aqueous solution. The results obtained from the variation of the activity with the incubation time highlight that the protein incubated in 12-10-12 has a high catalysis activity and a weakened conformational stability. The mechanism of the superactivity of α-CT in the presence of 12-10-12 has been proposed by combining the results from isothermaltitration calorimetry （ITC）, steady state fluorescence, and differential scanning calorimetry （DSC）. The superactivity arises from perturbation of the internal structure of α-CT by an interaction between the positively charged 12-10-12 and α-CT, which makes the conformation of α-CT looser than the native one, in the balance of a weak interaction. Such a conformation is favorable for release of the acidic product of 2-NA hydrolysis, whereas it simultaneously leads to instability of the α-CT structure.

关 键 词：表面活性剂 Α-糜蛋白酶 超活性 等温滴定量热 稳态荧光 差示扫描量热 

分 类 号：O629.8[理学—有机化学] O647.2[理学—化学]