双金属Hg^(2+)和Cu^(2+)对木瓜蛋白酶活性与构象的影响  

Effect of bimetal Hg^(2+) and Cu^(2+) on activity and conformation of papain

作　　者：张存滢[1] 曾虹燕[1] 熊龙斌[1] 刘学英[1] Gohi A 蔡西玲[1] 陈泽新 

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6期2207-2213,共7页Journal of Central South University:Science and Technology

基　　金：湖南省科技厅社会发展支撑计划(2011SK3138);湖南省研究生科研创新项目(CX2011B265)

摘　　要：研究双金属Hg2+和Cu2+对木瓜蛋白酶活性与构象的影响。利用FT-IR、荧光发射以及紫外吸收光谱探讨Hg2+和Cu2+处理与木瓜蛋白酶二级结构变化的关系。研究结果表明:金属离子与木瓜蛋白酶活性之间存在剂量效应关系,表现出低剂量促进,高剂量抑制的Hormesis现象。低浓度下,双金属Hg2+和Cu2+表现出协同激活效应;高浓度下,Cu2+的添加屏蔽了Hg2+的抑制作用。双金属离子浓度为10 6mol/L Hg2+和10-8mol/L Cu2+时,对酶的激活效应最大,其处理的木瓜蛋白酶的有序结构(α-螺旋和β-折叠)含量最高,二级结构最稳定,酶与底物亲和力最强,活性最高。当双金属离子浓度为10 4mol/L Hg2+和10-4mol/L Cu2+时,其抑制力最强,处理的木瓜蛋白酶有序结构含量最低,二级结构破坏,活性最低。木瓜蛋白酶分子构象的有序度与其活性呈正相关。The effect of the bimetal Hg^2＋ and Cu^2＋ on activity and conformation of papain was studied. The secondary structures of the papain treated by the bimetal ions were investigated by characterization using FT-IR, fluorescence emitting and ultraviolet-absorption spectra. The results show that there exists the dosage-response relationship between the metals and papain activity, which indicates that the bimetal ions have Hormesis effect on the activity known as ＂a low dose stimulation, high dose inhibition＂. Under low concentration, the bimetal ions exhibit synergistic activation effect on papain activity, and Cu^2＋ shields Hg^2＋ inhibition on the activity at high concentration. On the one hand, when the concentrations of Hg^2＋ and Cu^2＋ are 10-6 and 10-8 mol/L respectively, the strongest activity effect of the bimetal ions on papain is obtained. The content of the nonrandom secondary structures （a-helix and fl-sheet） of the treated papain is the highest with the secondary structures of papain being most stable, and enzymatic affinity strongest and papain activity being best. When the concentrations of Hg^2＋ and Cu^2＋ are 10^-4 mol/L, the ordered structure content and papain activity are the lowest. The bimetal ions unfold the enzymic protein and cause the destruction of the secondary structures. The order degree ofpapain conformation is correlated positively with the activity.

关 键 词：木瓜蛋白酶 双金属离子 构象 酶活性 

分 类 号：Q518.4[生物学—生物化学]