Knapp S, Ladenstein R, Galinski E A
Karolinska Institute, Department of Biosciences at Novum, Center for Structural Biochemistry (CSB), Huddinge, Sweden.
Extremophiles. 1999 Aug;3(3):191-8. doi: 10.1007/s007920050116.
Thermodynamic aspects of protein stabilization by two widespread naturally occurring osmolytes, beta-hydroxyectoine and betaine, were studied using differential scanning calorimetry (DSC) and bovine ribonuclease A (RNase A) as a model protein. The osmolyte beta-hydroxyectoine purified from Marinococcus was found to be a very efficient stabilizer. At a concentration of 3M it increased the melting temperature of RNase A (Tm) by more than 12K and gave rise to a stability increase of 10.6kJ/mol at room temperature. The heat capacity difference between the folded and unfolded state (deltaC(p)) was found to be significantly increased. Betaine stabilized RNase A only at concentrations less than 3M. Also, here deltaCp was found to be increased. Calculation of the number of water molecules that additionally bind to unfolded RNase A resulted in surprisingly low numbers for both osmolytes. The significant stabilization of RNase A by beta-hydroxyectoine makes this osmolyte an interesting stabilizer in biotechnological processes in which enzymes are applied in the presence of denaturants or at high temperature.
利用差示扫描量热法（DSC）并以牛核糖核酸酶A（RNase A）作为模型蛋白，研究了两种广泛存在的天然渗透剂β-羟基ectoine和甜菜碱对蛋白质的稳定作用的热力学方面。从海球菌中纯化得到的渗透剂β-羟基ectoine被发现是一种非常有效的稳定剂。在3M的浓度下，它使RNase A的解链温度（Tm）提高了超过12K，并在室温下使稳定性增加了10.6kJ/mol。发现折叠态与未折叠态之间的热容差（deltaC(p)）显著增加。甜菜碱仅在浓度低于3M时稳定RNase A。此外，在这里也发现deltaCp增加。计算额外结合到未折叠RNase A上的水分子数量，结果表明两种渗透剂的数量都惊人地低。β-羟基ectoine对RNase A的显著稳定作用使其成为生物技术过程中一种有趣的稳定剂，在这些过程中酶是在变性剂存在或高温下应用的。
