D'Auria S, Nucci R, Rossi M, Bertoli E, Tanfani F, Gryczynski I, Malak H, Lakowicz J R
Istituto di Biochimica delle Proteine ed Enzimologia, C.N.R., Via Marconi, 10 80125 Naples, Italy.
J Biochem. 1999 Sep;126(3):545-52. doi: 10.1093/oxfordjournals.jbchem.a022484.
beta-Glycosidase from the extreme thermophilic archaeon Sulfolobus solfataricus is a tetrameric protein with a molecular mass of 240 kDa, stable in the presence of detergents, and with a maximal activity at temperatures above 95 degrees C. Understanding the structure-activity relationships of the enzyme under different conditions is of fundamental importance for both theoretical and applicative purposes. In this paper we report the effect of methanol, ethanol, 1-propanol, and 1-butanol on the activity of S. solfataricus beta-glycosidase expressed in Escherichia coli. The alcohols stimulated the enzyme activity, with 1-butanol producing its maximum effect at a lower concentration than the other alcohols. The structure of the enzyme was studied in the presence of 1-butanol by circular dichroism, and Fourier-transform infrared and fluorescence spectroscopies. Circular dichroism and steady-state fluorescence measurements revealed that at low temperatures the presence of the alcohol produced no significant changes in the tertiary structure of the enzyme. However, time-resolved fluorescence data showed that the alcohol modifies the protein microenvironment, leading to a more flexible enzyme structure, which is probably responsible for the enhanced enzymatic activity.
来自极端嗜热古菌嗜热栖热菌的β-糖苷酶是一种分子量为240 kDa的四聚体蛋白，在洗涤剂存在下稳定，在高于95摄氏度的温度下具有最大活性。了解该酶在不同条件下的构效关系对于理论和应用目的都至关重要。在本文中，我们报告了甲醇、乙醇、1-丙醇和1-丁醇对在大肠杆菌中表达的嗜热栖热菌β-糖苷酶活性的影响。这些醇类刺激了酶的活性，其中1-丁醇在比其他醇类更低的浓度下产生最大效果。通过圆二色性、傅里叶变换红外光谱和荧光光谱在1-丁醇存在下研究了该酶的结构。圆二色性和稳态荧光测量表明，在低温下，醇类的存在对酶的三级结构没有显著影响。然而，时间分辨荧光数据表明，醇类改变了蛋白质微环境，导致酶结构更加灵活，这可能是酶活性增强的原因。
