De Bolle X, Vinals C, Fastrez J, Feytmans E
Laboratoire de Biologie Moléculaire Structurale, Unité de Recherche en Biologie Moléculaire, Facultés Universitaires Notre-Dame de la Paix, Rue de Bruxelles 61, B-5000 Namur, Belgium.
Biochem J. 1997 Apr 15;323 ( Pt 2)(Pt 2):409-13. doi: 10.1042/bj3230409.
The thermostability of yeast alcohol dehydrogenase (ADH) I is strongly dependent on the presence of NaCl, a salt that is almost neutral on the Hofmeister scale, which suggests that solvent-accessible electrostatic repulsion might play a role in the inactivation of the enzyme. Moreover, CaCl2 and MgCl2 are able to stabilize the enzyme at millimolar concentrations. Ca2+ stabilizes yeast ADH I by preventing the dissociation of the reduced form of the enzyme and by preventing the unfolding of the oxidized form of the enzyme. An analysis of several chimaeric ADHs suggests that Ca2+ is fixed by the Asp-236 and Glu-101 side chains in yeast ADH I, but that Ca2+ can be displaced by replacing Met-168 by an Arg residue, as suggested by a three-dimensional model of the enzyme structure. These results indicate that electrostatic repulsion can cause protein unfolding and/or dissociation. It is proposed that yeast ADH I binds Mg2+ in vivo.
酵母乙醇脱氢酶（ADH）I的热稳定性强烈依赖于NaCl的存在，NaCl在霍夫迈斯特序列中几乎呈中性，这表明溶剂可及的静电排斥可能在该酶的失活过程中起作用。此外，CaCl2和MgCl2能够在毫摩尔浓度下稳定该酶。Ca2+通过防止酶的还原形式解离以及防止酶的氧化形式展开来稳定酵母ADH I。对几种嵌合ADH的分析表明，Ca2+在酵母ADH I中由Asp-236和Glu-101侧链固定，但正如酶结构的三维模型所表明的，通过用Arg残基取代Met-168，Ca2+可以被取代。这些结果表明静电排斥可导致蛋白质展开和/或解离。有人提出酵母ADH I在体内结合Mg2+。
