Rajeshwara A N, Prakash V
Department of Protein Technology, Central Food Technological Research Institute, Mysore, India.
Int J Pept Protein Res. 1994 Nov;44(5):435-40. doi: 10.1111/j.1399-3011.1994.tb00179.x.
Purified lipase from wheat germ was used for the determination of preferential interaction parameters under different stabilizing cosolvent conditions. The partial specific volume of the enzyme was measured under both isomolal and isopotential conditions in phosphate buffer at pH 7.0, 0.02 M, and the value was found to be 0.730 +/- 0.001 and 0.731 +/- 0.002 mL/g, respectively. The partial specific volume measurements with different cosolvents indicated that the enzyme has a (delta g3/delta g2)T,mu1,mu3 values of -0.119 +/- 0.012, -0.073 +/- 0.009 and -0.141 +/- 0.020 g/g, respectively, in 25% glucose, 25% sucrose and 25% DMSO. The (delta g3/delta g2)T,mu1,mu3 values in 10 and 20% glycerol were -0.054 +/- 0.012 and -0.073 +/- 0.016 g/g, respectively. Based on these values it is clear that the enzyme is stabilized in the presence of these cosolvents by increasing its hydration, of which DMSO is stabilizing to the maximum extent. The stabilization of the enzyme was also confirmed by the thermal denaturation measurements in the presence of these cosolvents which indicated a shift in the apparent thermal denaturation temperature of the enzyme towards higher temperatures. The data are supported further by the ultraviolet difference spectral as well as fluorescence measurements in the presence of these cosolvents. The stabilization has been attributed to the preferential hydration of the enzyme in the presence of these cosolvents.
从小麦胚芽中纯化得到的脂肪酶用于测定不同稳定化助溶剂条件下的优先相互作用参数。在pH 7.0、0.02 M的磷酸盐缓冲液中，分别在等摩尔和等电位条件下测量了该酶的偏比容，发现其值分别为0.730±0.001和0.731±0.002 mL/g。用不同助溶剂进行的偏比容测量表明，在25%葡萄糖、25%蔗糖和25%二甲基亚砜中，该酶的（δg3/δg2）T,μ1,μ3值分别为-0.119±0.012、-0.073±0.009和-0.141±0.020 g/g。在10%和20%甘油中的（δg3/δg2）T,μ1,μ3值分别为-0.054±0.012和-0.073±0.016 g/g。基于这些值，很明显这些助溶剂通过增加酶的水合作用来稳定酶，其中二甲基亚砜的稳定作用最大。在这些助溶剂存在下进行热变性测量也证实了酶的稳定性，这表明酶的表观热变性温度向更高温度移动。这些助溶剂存在下的紫外差光谱以及荧光测量进一步支持了这些数据。这种稳定性归因于这些助溶剂存在下酶的优先水合作用。
