Rajendran S, Radha C, Prakash V
Department of Protein Technology, Central Food Technological Research Institute, Mysore, India.
Int J Pept Protein Res. 1995 Feb;45(2):122-8. doi: 10.1111/j.1399-3011.1995.tb01030.x.
The transition temperature of irreversible thermal inactivation of alpha-amylase from Bacillus amyloliquefaciens was estimated to be 60 degrees C. At this temperature, the enzyme inactivation followed first-order kinetics, having a half-life (t 1/2) of 12 min with a rate constant (k) of 0.06 min-1. Conformational change was a prerequisite for this thermal inactivation. This is governed by stepwise temperature-dependent phenomena. Among the solvent stabilizers tested, the enzyme was thermally stable in presence of DMSO and PEG 300 and the stabilizing efficiency of these cosolvents was concentration-dependent. The enzyme was partially stabilized by 5.0 M DMSO and 1.9 M PEG 300 up to 78 degrees C. However, above 78 degrees C the enzyme was inactivated in these cosolvents also. The mechanism of stabilization has been explained by preferential hydration of the enzyme in these structure stabilizing solvents by exclusion from the protein surface and interface by measurement of partial specific volume in these cosolvents. The data suggest a high value of preferential interaction parameter, (delta g3/delta g2)tau, mu 1, mu 3 being -0.606/g/g g/g in 40% DMSO and a low value of -0.025 g/g in 5% glycerol. The preferential interaction parameters in sucrose and glycerol suggests that (delta g3/delta g2)tau, mu 1, mu 3m is highest of -0.420 g/g in 10% glycerol than any other cosolvent.
解淀粉芽孢杆菌α-淀粉酶不可逆热失活的转变温度估计为60摄氏度。在此温度下，酶失活遵循一级动力学，半衰期（t1/2）为12分钟，速率常数（k）为0.06分钟-1。构象变化是这种热失活的先决条件。这受逐步的温度依赖性现象支配。在所测试的溶剂稳定剂中，酶在二甲基亚砜（DMSO）和聚乙二醇300（PEG 300）存在下具有热稳定性，并且这些共溶剂的稳定效率与浓度有关。该酶在5.0 M DMSO和1.9 M PEG 300存在下可部分稳定至78摄氏度。然而，在78摄氏度以上，该酶在这些共溶剂中也会失活。通过测量这些共溶剂中的偏比容，从蛋白质表面和界面排除水分子，从而在这些结构稳定溶剂中对酶进行优先水合，解释了稳定机制。数据表明，优先相互作用参数（δg3/δg2）τ、μ1、μ3在40% DMSO中为-0.606/g/g g/g，在5%甘油中为-0.025 g/g，数值较低。蔗糖和甘油中的优先相互作用参数表明，（δg3/δg2）τ、μ1、μ3m在10%甘油中为-0.420 g/g，高于任何其他共溶剂。
