pH值对芽孢皮层裂解酶活性及结构的影响

为探究酸性pH值条件抑制芽孢萌发的机理,研究了不同pH值处理对芽孢皮层裂解酶(CwlJ)的活性和结构的影响。采用傅立叶红外光谱法与荧光光谱法来分析芽孢皮层裂解酶(CwlJ)的二、三级结构与酶的活性之间的关系。实验所采用的pH值为3、5、7、9、11,结果表明:1)p H值为3、5时,随着时间的推移,芽孢皮层裂解酶(CwlJ)被激活,活性很高;2)酶的活性与其二级结构域中的α-螺旋相对含量紧密相关;当pH值从3增加到5时,α-螺旋相对含量不断增大,由36.15%增加到37.29%,当pH值从5增加到7时,α-螺旋相对含量基本不变,当pH值从7增加到11时,α-螺旋相对含量不断的减小,即在pH值为3～5之间酶可能被激活;3)随着pH处理条件的改变,pH值为5的荧光强度最强,内部蛋白质完全展开,空间结构更加松散扩张,三级结构更加稳定。结果表明,在酸性pH值条件下,皮层裂解酶(CwlJ)的结构稳定,活性高,故推测酸对芽孢萌发的抑制作用不是因为其抑制了皮层裂解酶的活性。

Effects of pH Treatments on the Activity and Structure of Cortical Lyase in Spores

In order to explore the inhibitory mechanism of acidic pH conditions for spore germination, the study investigated effects of different pH treatments on the activity and structure of spore cortical lyase (CwlJ). Using Fourier transform infrared spectroscopy and fluorescence spectroscopy, the relationship between the secondary and tertiary structures of CwlJ and its activity was analyzed. The pH values were set to 3, 5, 7, 9 and 11 in the experiment. The results showed that: 1) CwlJ was activated over time with pH 3 and 5; 2) The activity of CwlJ was closely related to the content of alpha-helix in its secondary structure; when pH value increased from 3 to 5, the content of alpha-helix also increased from 36.15% to 37.29%; when pH increased from 5 to 7, the content of alpha-helix basically unchanged; when pH increased from 7 to 11, the content of alpha-helix decreased; therefore, the enzyme may be activated in the pH range of 3-5; 3) the fluorescence intensity in pH 5 was strongest, the internal protein was fully unfolded, and the spatial structure was more loosely expanded, and the tertiary structure was more stable. In conclusion, the structure of CwlJ was stable and its activity was high in acidic pH conditions, so it was speculated that the inhibition of acidity for spore germination was not due to its inhibition for the activity of cortical lyase.