十二烷基硫酸钠对木瓜酶酶活性和构象的影响

Effect of SDS on Activity and Conformation of Papain

采用紫外、荧光和圆二色等光谱技术研究了阴离子表面活性剂十二烷基硫酸钠(SDS)对木瓜酶酶活力及其构象变化的影响。结果表明:(1)SDS对木瓜酶酶活力的影响与pH有关,pH=8.00时,SDS对木瓜酶酶活力有增强作用,pH=6.30时,除了在SDS的临界胶束浓度(cmc)时木瓜酶酶活力得到增强外,其他浓度下SDS对木瓜酶酶活力没有影响,pH=9.50时,SDS对木瓜酶酶活力产生抑制作用。(2)SDS对木瓜酶的荧光产生淬灭,0.1cmc的SDS木瓜酶荧光峰红移,而SDS浓度1cmc后则使之蓝移;(3)当[SDS]<cmc时,木瓜酶的A-螺旋、B-折叠、回转等有序结构的含量减少而无定形结构含量增加,当[SD S]>cmc后,木瓜酶的A-螺旋、B-折叠构型含量有所增加,无定形构型含量则有所减少。有序结构的含量越大,酶活力越强。

The effect of Sodium dodecyl sulfate （SDS） on activity and conformation of papain enzyme was studied by UV-Vis Spectroscopy,Fluorescence Spectroscopy and Circular Dichroism（CD） spectroscopy. Results showed that ： （1） the effect of SDS on activity of papain enzyme was related to pH value,it displayed an activate effect on activity of papain enzyme at pH8. 00 but caused inhibition at pH 9.50,and at pH6.30,there was not influence except in the critic mlcelle concentration （cmc） of SDS, in this concentration,the activity of papain enzyme increased ; （2） the fluorescence spectrum shown that SDS had an ability to quench the papain fluorescence,when SDS concentration was 0.1 cmc, the fluorescence spectrum appeared red-shift, while SDS concentration;〉 lcmc, it appeared blue shift; （3） for the secondary conformation,the CD spectrum indicated that when SDS concentration was lower than cmc, the content of conformations such as a-helix,γ-sheet and turning decreased,while the content of disorder conformation increased. When SDS concentration was cmc above,the content of ce-helix and p-sheet conformations increased,and the content of turning and disorder conformations decreased. The higher the proportion of ordered structure was, the higher the enzyme activity was.