【摘要】 长期以来 ,如何提高酶蛋白的热稳定性是分子生物学、生物工程学、化学工业等所关注的重要研究课题之一。分析了多种无机离子、糖和氨基酸对枯草杆菌液化型α 淀粉酶热稳定性的影响以及它们的共存效应 ,获取了一些对相关研究领域具有理论参考和实际应用价值的实验结果。在无机盐中 ,1mmol L的钙离子或 5 0mmol L的钠离子能显著地提高该酶的热稳定性 ;酸性氨基酸和碱性氨基酸表现出相反的结果 :酸性氨基酸具有明显的增强作用 ,碱性氨基酸却使之降低 ;随着糖浓度的增加 (0～ 10 0 0mmol L) ,该淀粉酶的热稳定性呈线性增高 ;当钠离子或钾离子与某些氨基酸或糖类共同存在时 ,对该淀粉酶的热稳定性表现出了明显的协同作用。试图通过检测酶蛋白分子荧光强度改变来反映该酶的热稳定性变化 ,其结果是 :随着温度的改变 ,酶蛋白的荧光强度的衰减与残余酶活性之间显示了良好的相关性。从而说明热环境使酶蛋白分子的螺旋结构发生变化而失活 ,某些溶质的存在可能是通过作用于蛋白质分子的立体结构而影响该酶的热稳定性。更多还原

【Abstract】 Supplement effects of ions, sugars, and amino acids on the thermostability of liquefying type α-amylase from Bacillus subtilis were examined. The addition of 1 mmol/L Ca 2 or about 50 mmol/L Na remarkably stimulated the thermostabi| lity of this enzyme among ions examined. The thermostability of the enzyme was enhanced and reduced by the extrinsic addition of 50 mmol/L acidic amino acid such as glutamic acid and alkaline amino acid such as arginine, respectively. With the increases of the concentrations of sugars from 0 to 1000 mmol/L the thermostability of α-amylase increased almost linearly. By the co-existence of Na or K with some amino acids or sugars the thermostability of this enzyme was fairly increased. The changes in the fluorescence intensity of α-amylase were examined as a function of the incubation temperature on the enzyme, which showed a good agreement with those of residual activities.更多还原