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采用荧光光谱、圆二色谱(CD)和紫外光谱研究了十六烷基三甲基溴化铵(CTAB)在NaHPO_4-NaH_2PO_4缓冲溶液中对木瓜酶构象变化及其酶活的影响,并探讨了CTAB与木瓜酶的作用机理。荧光光谱表明.在CTAB存在下,木瓜酶的荧光强度增强.荧光峰发生红移,CTAB使木瓜酶分子链趋于伸展,酪氨酸等发色基团更多地暴露在水中。CD谱表明.当CTAB浓度(C_(CTAB))为0.5 mmol/L时,木瓜酶的α-螺旋构象和β-折叠构象含量比纯木瓜酶(Papain)体系分别增加了1.3%和0.1%,回转构象和无定型构象含量则分别减少了0.3%和1.2%。酶活测定结果表明,CTAB对木瓜酶的酶活有较大影响。当C_(CTAB)由0增加到1.5mmol/L时,木瓜酶酶活由11.2×10~5U/g增大到16.3×10~5U/g,当C_(CTAB)由1.5mmol/L增加到3.5mmol/L,木瓜酶的酶活又由峰值(16.3×10~5U/g)降到11.7×10~5U/g,CTAB使木瓜酶酶活增强与木瓜酶的构象有序度提高有关。
The effect of cetyltrimethylammonium bromide (CTAB) on the conformational change and enzyme activity of papain in NaHPO_4-NaH_2PO_4 buffer solution was investigated by fluorescence spectroscopy, circular dichroism spectroscopy (CD) and ultraviolet spectroscopy CTAB and papaya enzyme mechanism of action. Fluorescence spectra showed that in the presence of CTAB, the fluorescence intensity of papain increased, the fluorescence peak red-shifted, CTAB to papaya enzyme chain tends to stretch, tyrosine and other chromophores more exposed to water. CD spectra showed that the α-helical conformation and the β-sheet conformational content of Papain increased by 1.3% and 0.1%, respectively, when compared with the Papain system at a CTAB concentration of 0.5 mmol / L, Rotational conformation and amorphous conformation decreased by 0.3% and 1.2% respectively. The results of enzyme activity assay showed that CTAB had a significant effect on papain enzyme activity. When C_ (CTAB) increased from 0 to 1.5mmol / L, papain activity increased from 11.2 × 10 ~ 5U / g to 16.3 × 10 ~ 5U / g, while CTAB increased from 1.5mmol / L to 3.5 mmol / L and papain activity decreased from 16.3 × 10-5 U / g to 11.7 × 10-5 U / g, respectively. CTAB increased the activity of papain and the conformational order of papain.