Lyubarev A E, Kurganov B I, Burlakova A A, Orlov V N
Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russian Federation.
Biophys Chem. 1998 Mar 9;70(3):247-57. doi: 10.1016/s0301-4622(97)00133-6.
Thermal denaturation of uridine phosphorylase from Escherichia coli K-12 has been studied by differential scanning calorimetry. The excess heat capacity vs. temperature profiles were obtained at temperature scanning rates of 0.25, 0.5, and 1 K/min. These profiles were analysed using three models of irreversible denaturation which are approximations to the whole Lumry-Eyring model, namely, the one-step model of irreversible denaturation, the Lumry-Eyring model with the fast equilibrating first step, and the model involving two consecutive irreversible steps. In terms of statistics the latter model describes the kinetics of thermal denaturation of uridine phosphorylase more satisfactorily than the two other models. The values of energy activation for the first and second steps calculated for the model involving two consecutive irreversible steps are the following: Ea,1 = 609.3 +/- 1.8 kJ/mol and Ea,2 = 446.8 +/- 3.2 kJ/mol.
利用差示扫描量热法研究了大肠杆菌K-12尿苷磷酸化酶的热变性。在0.25、0.5和1 K/min的温度扫描速率下获得了过量热容与温度的关系曲线。使用三种不可逆变性模型对这些曲线进行了分析，这三种模型是对整个Lumry-Eyring模型的近似，即不可逆变性的一步模型、第一步快速平衡的Lumry-Eyring模型以及涉及两个连续不可逆步骤的模型。从统计学角度来看，后一种模型比其他两种模型更能令人满意地描述尿苷磷酸化酶的热变性动力学。为涉及两个连续不可逆步骤的模型计算的第一步和第二步的活化能值如下：Ea,1 = 609.3 +/- 1.8 kJ/mol，Ea,2 = 446.8 +/- 3.2 kJ/mol。
