Fujita Y, Noda Y
Department of Chemistry, Hyogo College of Medicine, Japan.
Int J Pept Protein Res. 1992 Aug;40(2):103-9. doi: 10.1111/j.1399-3011.1992.tb01456.x.
The amino groups of hen egg white lysozyme were reductively alkylated by the reaction with aliphatic aldehydes of various chain lengths and with two aldehydes of different steric hindrance at pH 7.5 and 4 degrees for 3 h. About four of the original six lysine residues were modified by the reaction with acetaldehyde, n-butylaldehyde or n-hexylaldehyde. About three lysine residues were 2,2-dimethylpropylated with trimethylacetaldehyde while a single residue was modified with benzaldehyde. The thermal stabilities of these alkylated lysozymes were investigated by differential scanning calorimetry (DSC) at different acidic pH values. Alkylation thermally destabilized the proteins, depending not only on the extent of modification but also on the size of the substituent. The alkylated derivatives were 8-19 kJ/mol less stable than native lysozyme at 25 degrees and pH 3.0. The temperature dependences of the activities of the alkylated lysozymes against ethylene glycol chitin indicated that the orders of the optimum temperatures and the maximum activities were exactly the same as the order of the thermal stabilities.
在pH 7.5和4℃条件下，将蛋清溶菌酶的氨基与不同链长的脂肪醛以及两种具有不同空间位阻的醛反应3小时，进行还原烷基化。与乙醛、正丁醛或正己醛反应时，原来六个赖氨酸残基中约有四个被修饰。约三个赖氨酸残基被三甲基乙醛进行2,2 - 二甲基丙基化，而单个残基被苯甲醛修饰。通过差示扫描量热法（DSC）在不同酸性pH值下研究了这些烷基化溶菌酶的热稳定性。烷基化使蛋白质在热稳定性上降低，这不仅取决于修饰程度，还取决于取代基的大小。在25℃和pH 3.0条件下，烷基化衍生物的稳定性比天然溶菌酶低8 - 19 kJ/mol。烷基化溶菌酶对乙二醇几丁质的活性温度依赖性表明，最佳温度和最大活性的顺序与热稳定性顺序完全相同。
