Hg^(2+)对木瓜蛋白酶的修饰作用及其动力学  

Modification effect of Hg^(2+) on papain and its kinetics

作　　者：蔡西玲[1] 曾虹燕[1] 蔡联辉[1] 何平[1] 张存滢[1] 刘学英[1] 吴雅兰[1] 

机构地区：[1]湘潭大学化工学院,湖南湘潭411105

出　　处：《中南大学学报（自然科学版）》2013年第10期3991-3997,共7页Journal of Central South University:Science and Technology

基　　金：湖南省科技厅计划项目(2011SK3138);湖南省研究生科研创新项目(CX2011B265);湘潭大学大学生创新项目(2012年)

摘　　要：通过对Hg2+处理的木瓜蛋白酶FT-IR图谱中的酰胺Ⅰ带进行去卷积和曲线拟合,结合荧光光谱技术,对其进行二级结构分析。运用邹氏酶活性不可逆改变动力学理论,研究酶与Hg2+结合的动力学规律,探索Hg2+对木瓜蛋白酶活性的作用机理。研究结果表明:Hg2+对木瓜蛋白酶具激活和抑制的双重作用,Hg2+对木瓜蛋白酶作用表现出低促高抑的Hormesis现象。酶活主要取决于其活性中心位构象,尤其是无规则卷曲和β-转角。β-转角含量减少,无规则卷曲含量增加,有助于酶活提高,反之酶活降低。低浓度下(10 6mol/L)Hg2+对木瓜蛋白酶的作用为非竞争性不可逆激活,酶活增大;高浓度下(10 4mol/L)Hg2+对酶的抑制作用以竞争性抑制为主,酶活降低。The secondary structures of the papain treated by Hg^2＋ were determined by FT-IR in amide-I region band using Fourier deconvolution and curve-fitting technique and fluorescence emission spectra. Based on Tsou＇s theory on the kinetics of irreversible modification of enzymic activity, the kinetics of the reaction of Hg^2＋ with papain was studied in order to explore the mechanism of Hg^2＋ on papain. The results show that Hg^2＋ has active and inhibitory effect on papain, and the effect of Hg^2＋ on papain in the tyrosine hydrolytic reaction shows the Hormesis effect. The activity of papain depends crucially on the active site conformation, especially of β-tum and random. The papain activity is increased when the amounts of β-turn decrease or with random increase in papain, and vice versa. At low Hg^2＋ concentration of 10^-6 mol/L, Hg^2＋ is efficacious activator, and effect is classified as noncompetitive type. Under high concentration of 10^-4 mol/L, the inhibition of Hg^2＋ on the enzyme is found to be largely of competitive type.

关 键 词：木瓜蛋白酶 Hg2+ 动力学 酶活 二级结构 不可逆修饰 

分 类 号：TQ028.8[化学工程]