中华猕猴桃蛋白酶在乙醇溶液中的分子折叠

The Molecular Folding of Actinidin in Ethanol Solutions

研究了中华猕猴桃蛋白酶在不同浓度（Ｖ：Ｖ）乙醇存在下的内源荧光发射光谱、紫外差光谱、圆二色光谱（ＣＤ谱）及傅立叶变换红外光谱的变化，并测定了相应的活力变化，当乙醇浓度低于３０％时，酶的荧光强度无明显变化，而乙醇浓度大于３０％时，则酶荧光强度增大，且峰位略红移。在乙醇溶液中，酶的紫外差光谱在２２５～２３５ｎｍ内出现正峰，峰强度随乙醇浓度的增高基本表现为逐渐增大，峰位也逐渐蓝移。ＣＤ谱及红外光谱的测定结果表明低浓度乙醇中酶分子有序二级结构的减少及高浓度乙醇中β－折叠含量的增加．随乙醇浓度的增加．酶的活力表现为逐渐降低，且乙醇对酶的失活作用类似于竞争性抑制。

Changes of conformation of Actinidin in different concentrations(V:v)ofethanol solution had been studied by means of measuring the fluorescence emission spectra,dif-ferential UV-absorbance spectra,circular dichroic spectra CD and Fourier transform infraredspectra(FTIR).The correspondent enzyme activities were also measured.No changes of the flu-orescence intensitv of the enzyme could be detected when ethanol concentrations were below30%。 But when ethanol concentrations were above 30%,the fluorescence intensity of the enzymeincreased with the increase of ethanol concentration,and the fluorescence emission peaks ap-peared red-shifted.The differential UV-absorbance spectra showed that there was a positive peakin the range of 225～235 nm,the intensity of the peak increased with increasing ethanol concen-tration,and the peak position appeared blue-shifted. The CD and FTIP spectra showed that theordered secondary structures of Actinidin reduced in lower concentrations of ethanol,whereas theβ-sheet structures of the enzyme increased in higher concentrations of ethanol.The enzyme activ-ity decreased with the increase of ethanol concentration,and the inactivation mechanism was sim-ilar to the competitive inhipition.