Yeast alcohol dehydrogenase structure and catalysis.
Yeast alcohol dehydrogenase structure and catalysis.
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DOI：
10.1021/bi5006442
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发表时间：
2014-09-16
期刊：
影响因子：
2.9
通讯作者：
Plapp, Bryce V.
中科院分区：
文献类型：
--
作者：
Raj, Savarimuthu Baskar;Ramaswamy, S.;Plapp, Bryce V.
酵母（酿酒酵母）乙醇脱氢酶 I (ADH1) 是葡萄糖发酵过程中将乙醛还原为乙醇的组成酶。 ADH1 是具有 347 个氨基酸残基的亚基同源四聚体。 ADH1 的结构通过 X 射线晶体学以 2.4 Å 分辨率确定。不对称单元包含四个不同的亚基，排列为类似的二聚体，称为 AB 和 CD。该晶胞包含由“背靠背”二聚体 AB:AB 和 CD:CD 组成的两个不同的四聚体。每个二聚体中的 A 和 C 亚基结构相似，具有闭合构象、结合辅酶，2,2,2-三氟乙醇的氧以与 Cys-43、Cys-153 和 His-66 的经典四面体配位方式与催化锌连接。相比之下，B 和 D 亚基具有开放构象，没有结合辅酶，催化锌与 Cys-43、Cys-153、His-66 和 Glu-67 的羧酸盐具有替代的反向配位。四聚体的二聚亚基的不对称性提供了两种似乎与催化机制相关的结构。锌的替代配位可能代表用醇或醛底物置换锌结合水的机制中的中间体。用 Gln-67 替代 Glu-67 会使催化效率降低 100 倍。先前对结构建模、进化关系、底物特异性、化学修饰和定点诱变的研究通过三维结构得到了更全面的解释。
Yeast (Saccharomyces cerevisiae) alcohol dehydrogenase I (ADH1) is the constitutive enzyme that reduces acetaldehyde to ethanol during the fermentation of glucose. ADH1 is a homotetramer of subunits with 347 amino acid residues. A structure for ADH1 was determined by X-ray crystallography at 2.4 Å resolution. The asymmetric unit contains four different subunits, arranged as similar dimers named AB and CD. The unit cell contains two different tetramers made up of “back-to-back” dimers, AB:AB and CD:CD. The A and C subunits in each dimer are structurally similar, with a closed conformation, bound coenzyme, and the oxygen of 2,2,2-trifluoroethanol ligated to the catalytic zinc in the classical tetrahedral coordination with Cys-43, Cys-153, and His-66. In contrast, the B and D subunits have an open conformation with no bound coenzyme, and the catalytic zinc has an alternative, inverted coordination with Cys-43, Cys-153, His-66, and the carboxylate of Glu-67. The asymmetry in the dimeric subunits of the tetramer provides two structures that appear to be relevant for the catalytic mechanism. The alternative coordination of the zinc may represent an intermediate in the mechanism of displacement of the zinc-bound water with alcohol or aldehyde substrates. Substitution of Glu-67 with Gln-67 decreases the catalytic efficiency by 100-fold. Previous studies of structural modeling, evolutionary relationships, substrate specificity, chemical modification, and site-directed mutagenesis are interpreted more fully with the three-dimensional structure.
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