Conformational changes and catalysis by alcohol dehydrogenase.
Conformational changes and catalysis by alcohol dehydrogenase.
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DOI：
10.1016/j.abb.2009.07.001
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发表时间：
2010-01-01
影响因子：
3.9
通讯作者：
Plapp BV
中科院分区：
文献类型：
--
作者：
Plapp BV
X射线晶体学显示，马肝醇脱氢酶在与NAD+或NADH结合后会发生整体构象变化，包括催化结构域相对于辅酶结合结构域的旋转以及活性位点的闭合，从而产生催化有效的酶。构象变化需要完整的辅酶，并受到各种化学或突变取代的影响，这些取代可以通过改变辅酶异构化动力学和解离速率来增加催化周转。 NAD+ 的结合在动力学上受到单分子异构化（对应于构象变化）的限制，该异构化由催化锌水的去质子化控制，产生带负电的氢氧化锌，它可以吸引带正电的烟酰胺环。 His-51 通过氢键网络将质子传递给溶剂，从而促进去质子化。 NADH的结合也涉及构象变化，但速度非常快。酶与 NAD+ 结合并关闭后，底物取代与催化锌结合的氢氧化物；这种交换可能涉及双置换反应，其中谷氨酸残基的羧基首先置换氢氧化物（反转锌的四面体配位），然后外源配体置换谷氨酸。产生的酶-NAD+-醇复合物准备进行氢转移，小的构象波动可能使反应物聚集在一起，从而通过量子力学隧道效应转移氢负离子。在此过程中，烟酰胺环可能会变得褶皱，如酶与 NADH 复合物的结构所示。乙醇脱氢酶的构象变化证明了蛋白质动力学在催化中的重要性。
As shown by X-ray crystallography, horse liver alcohol dehydrogenase undergoes a global conformational change upon binding of NAD+ or NADH, involving a rotation of the catalytic domain relative to the coenzyme binding domain and the closing up of the active site to produce a catalytically efficient enzyme. The conformational change requires a complete coenzyme and is affected by various chemical or mutational substitutions that can increase the catalytic turnover by altering the kinetics of the isomerization and rate of dissociation of coenzymes. The binding of NAD+ is kinetically limited by a unimolecular isomerization (corresponding to the conformational change) that is controlled by deprotonation of the catalytic zinc-water to produce a negatively-charged zinc-hydroxide, which can attract the positively-charged nicotinamide ring. The deprotonation is facilitated by His-51 acting through a hydrogen-bonded network to relay the proton to solvent. Binding of NADH also involves a conformational change, but the rate is very fast. After the enzyme binds NAD+ and closes up, the substrate displaces the hydroxide bound to the catalytic zinc; this exchange may involve a double displacement reaction where the carboxylate group of a glutamate residue first displaces the hydroxide (inverting the tetrahedral coordination of the zinc), and then the exogenous ligand displaces the glutamate. The resulting enzyme-NAD+-alcoholate complex is poised for hydrogen transfer, and small conformational fluctuations may bring the reactants together so that the hydride ion is transferred by quantum mechanical tunneling. In the process, the nicotinamide ring may become puckered, as seen in structures of complexes of the enzyme with NADH. The conformational changes of alcohol dehydrogenase demonstrate the importance of protein dynamics in catalysis.
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影响因子：
4.1
作者：
DALZIEL, K;DICKINSON, FM
通讯作者：
DICKINSON, FM
影响因子：
15
作者：
Billeter, SR;Webb, SP;Hammes-Schiffer, S
通讯作者：
Hammes-Schiffer, S
DOI：
10.1111/j.1432-1033.1984.tb08036.x
发表时间：
1984-01-01
期刊：
EUROPEAN JOURNAL OF BIOCHEMISTRY
影响因子：
--
作者：
ANDERSSON, P;KVASSMAN, J;PETTERSSON, G
通讯作者：
PETTERSSON, G
影响因子：
3.9
作者：
BRANDEN, CI
通讯作者：
BRANDEN, CI
影响因子：
2.9
作者：
Colby, TD;Bahnson, BJ;Goldstein, BM
通讯作者：
Goldstein, BM