Ahmad F, McPhie P
Biochemistry. 1978 Jan 24;17(2):241-6. doi: 10.1021/bi00595a008.
The denaturation of swine pepsinogen has been studied as a function of urea concentration, pH, and temperature. The unfolding of the protein by urea has been found to be fully reversible under different conditions of pH, temperature, and denaturant concentration. Kinetic experiments have shown that the transition shows two-state behavior at 25 degrees C in the pH range 6-8 covered in this study. Analysis of the equilibrium data obtained at 25 degrees C according to Tanford (Tanford, C. (1970), Adv. Protein Chem. 24, 1) and Pace (Pace, N.C. (1975), Crit. Rev. Biochem. 3, 1) leads to the conclusion that the free energy of stabilization of native pepsinogen, relative to the denatured state, under physiological conditions, is only 6-12 kcal mol-1. The temperature dependence of the equilibrium constant for the unfolding of pepsinogen by urea in the range 20-50 degrees C at pH 8.0 can be described by assigning the following values of thermodynamic parameters for the denaturation at 25 degrees C: deltaH=31.5 kcal mol-1; deltaS=105 cal deg-1 mol-1; and deltaCp=5215 cal deg-1 mol-1.
已对猪胃蛋白酶原的变性进行了研究，该研究将其作为尿素浓度、pH值和温度的函数。研究发现，在不同的pH值、温度和变性剂浓度条件下，尿素诱导的蛋白质去折叠是完全可逆的。动力学实验表明，在本研究涵盖的25℃、pH值6 - 8范围内，该转变呈现两态行为。根据坦福德（Tanford, C. (1970), Adv. Protein Chem. 24, 1）和佩斯（Pace, N.C. (1975), Crit. Rev. Biochem. 3, 1）的方法，对在25℃下获得的平衡数据进行分析，得出结论：在生理条件下，天然猪胃蛋白酶原相对于变性状态的稳定化自由能仅为6 - 12千卡/摩尔。在pH值8.0、20 - 50℃范围内，尿素诱导猪胃蛋白酶原去折叠的平衡常数与温度的关系，可以通过赋予25℃下变性的以下热力学参数值来描述：ΔH = 31.5千卡/摩尔；ΔS = 105卡/开尔文·摩尔；以及ΔCp = 5215卡/开尔文·摩尔。
