Structure of mitochondrial aldehyde dehydrogenase: The genetic component of ethanol aversion
Structure of mitochondrial aldehyde dehydrogenase: The genetic component of ethanol aversion
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DOI：
10.1016/s0969-2126(97)00224-4
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发表时间：
1997-05-15
期刊：
影响因子：
5.7
通讯作者：
Hurley, TD
中科院分区：
文献类型：
--
作者：
Steinmetz, CG;Xie, PG;Hurley, TD
背景：与减少饮酒和酗酒发病率最密切相关的单一遗传因素是线粒体乙醛脱氢酶（ALDH2）的自然发生变体。该变体在 487 位 (E487K) 处包含谷氨酸至赖氨酸的取代。 ALDH2 的 E487K 变体存在于大约 50% 的亚洲人群中，并且与杂合子和纯合子中 ALDH2 活性的表型丧失相关。缺乏 ALDH2 的个体对乙醇消耗表现出不良反应，这可能是由于血液乙醛水平升高所致。 ALDH2 的结构对于阐明其催化机制、清楚地了解 ALDH2 对酒精中毒遗传成分的贡献以及开发特定 ALDH2 抑制剂作为治疗酒精中毒的潜在药物具有重要意义。 结果：牛 ALDH2 的 X 射线结构已解析为游离形式的 2.65 埃和与 ALDH2 形成的复合物的 2.75 埃。辅酶A(+)。该酶结构包含三个结构域：两个二核苷酸结合结构域和一个小的三链β-折叠结构域，该结构域参与该四聚体酶中的亚基相互作用。 E487K 突变发生在这个小的寡聚结构域中，位于另一个单体活性位点正下方的亚基之间的关键界面处。 ALDH2的活性位点被NAD(+)的烟酰胺环分成两半。与烟酰胺环的 A 侧 (Pro-R) 相邻的是三个半胱氨酸簇 (Cys301、Cys302 和 Cys303)，与 B 侧 (Pro-S) 相邻的是 Thr244、Glu268、Glu476 以及与 Thr244 和 Glu476 结合的有序水分子。结论：虽然存在可识别的 Rossmann 型折叠，但ALDH2 的辅酶结合区以其他 NAD(+) 结合酶中未见的方式结合 NAD(+)。 NAD(+)烟酰胺环附近残基的位置表明了一种化学机制，其中Glu268通过结合的水分子充当通用碱基。 Asn169 的侧链酰胺氮和 Cys302 的肽氮处于适当位置，可在氢化物转移之前稳定四面体过渡态中存在的氧阴离子。残基 Glu487 的功能重要性现在看来是由于该残基通过 Arg264 和 Arg475 与底物结合位点的间接相互作用。
Background: The single genetic factor most strongly correlated with reduced alcohol consumption and incidence of alcoholism is a naturally occurring variant of mitochondrial aldehyde dehydrogenase (ALDH2). This Variant contains a glutamate to lysine substitution at position 487 (E487K). The E487K variant of ALDH2 is found in approximately 50% of the Asian population, and is associated with a phenotypic loss of ALDH2 activity in both heterozygotes and homozygotes. ALDH2-deficient individuals exhibit an averse response to ethanol consumption, which is probably caused by elevated levels of blood acetaldehyde. The structure of ALDH2 is important for the elucidation of its catalytic mechanism, to gain a clear understanding of the contribution of ALDH2 to the genetic component of alcoholism and for the development of specific ALDH2 inhibitors as potential drugs for use in the treatment of alcoholism.Results: The X-ray structure of bovine ALDH2 has been solved to 2.65 Angstrom in its free form and to 2.75 Angstrom in a complex with NAD(+). The enzyme structure contains three domains: two dinucleotide-binding domains and a small three-stranded beta-sheet domain, which is involved in subunit interactions in this tetrameric enzyme. The E487K mutation occurs in this small oligomerization domain and is located at a key interface between subunits immediately below the active site of another monomer. The active site of ALDH2 is divided into two halves by the nicotinamide ring of NAD(+). Adjacent to the A-side (Pro-R) of the nicotinamide ring is a cluster of three cysteines (Cys301, Cys302 and Cys303) and adjacent to the B-side (Pro-S) are Thr244, Glu268, Glu476 and an ordered water molecule bound to Thr244 and Glu476.Conclusions: Although there is a recognizable Rossmann-type fold, the coenzyme-binding region of ALDH2 binds NAD(+) in a manner not seen in other NAD(+)-binding enzymes. The positions of the residues near the nicotinamide ring of NAD(+) suggest a chemical mechanism whereby Glu268 functions as a general base through a bound water molecule. The sidechain amide nitrogen of Asn169 and the peptide nitrogen of Cys302 are in position to stabilize the oxyanion present in the tetrahedral transition state prior to hydride transfer. The functional importance of residue Glu487 now appears to be due to indirect interactions of this residue with the substrate-binding site via Arg264 and Arg475.