Genest M, Ptak M
Int J Pept Protein Res. 1982 Apr;19(4):420-31. doi: 10.1111/j.1399-3011.1982.tb02624.x.
Empirical theoretical calculations have been performed on a simplified model of the active site of two serine proteases: alpha-chymotrypsin and subtilisin Novo. The stability of the catalytic triad and the hydrogen bond formation between the Asp-His and His-Ser pairs have been examined for different protonation states. The results show that the Asp-His interactions prevail upon the His-Ser ones. Agreement between calculated configurations and the crystal structure of the site suggests that the presence of other residues near the functional residues is not determinant for the stability of the triad in alpha-chymotrypsin. In subtilisin Novo, on the contrary, the presence of the neighbouring residues seems to contribute more largely to the stability. Strong hydrogen bond interactions between the His and Ser residues do not exist in the resting enzymes. Any improvement of the His-Ser interactions requires large destabilization of the Asp-His diad. Our results suggest that the mechanism of the proton transfer can occur only from perturbations of the active site structure induced by the presence of the substrate.
已对两种丝氨酸蛋白酶（α-胰凝乳蛋白酶和枯草杆菌蛋白酶Novo）活性位点的简化模型进行了经验理论计算。针对不同的质子化状态，研究了催化三联体的稳定性以及天冬氨酸-组氨酸和组氨酸-丝氨酸对之间的氢键形成。结果表明，天冬氨酸-组氨酸相互作用比组氨酸-丝氨酸相互作用更占优势。计算构型与该位点晶体结构之间的一致性表明，在α-胰凝乳蛋白酶中，功能残基附近其他残基的存在对于三联体的稳定性并非决定性因素。相反，在枯草杆菌蛋白酶Novo中，相邻残基的存在似乎对稳定性有更大贡献。在静止酶中，组氨酸和丝氨酸残基之间不存在强氢键相互作用。组氨酸-丝氨酸相互作用的任何改善都需要天冬氨酸-组氨酸二联体的大幅去稳定化。我们 的结果表明，质子转移机制只能通过底物存在引起的活性位点结构扰动而发生。
