Human liver alcohol dehydrogenase: amino acid substitution in the beta 2 beta 2 Oriental isozyme explains functional properties, establishes an active site structure, and parallels mutational exchanges in the yeast enzyme.
Human liver alcohol dehydrogenase: amino acid substitution in the beta 2 beta 2 Oriental isozyme explains functional properties, establishes an active site structure, and parallels mutational exchanges in the yeast enzyme.
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人肝乙醇脱氢酶：β2β2东方同工酶中的氨基酸取代解释了功能特性，建立了活性位点结构，并与酵母酶中的突变交换相似。
DOI：
10.1073/pnas.81.10.3024
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发表时间：
1984
影响因子：
11.1
通讯作者：
Li,TK
中科院分区：
文献类型：
--
作者：
Jörnvall,H;Hempel,J;Vallee,BL;Bosron,WF;Li,TK
研究了人肝乙醇脱氢酶的同型二聚体东方β 2 β 2同工酶，对应于ADH 2基因位点的等位基因变体，以确定与高加索人中主要等位基因形式β 1 β 1同工酶相关的氨基酸交换。序列分析表明，氨基酸取代发生在最大的CNBr片段的第7位，对应于整个蛋白质链的第47位。在此，β 2型具有组氨酸残基，而与其他表征的哺乳动物肝脏醇脱氢酶一样，β 1型具有精氨酸残基。这种交换不会影响相邻的半胱氨酸-46残基，该残基是活性位点锌原子的蛋白质配体，从而澄清了之前不一致的结果。组氨酸/精氨酸-47突变替换对应于结合辅酶NAD（H）的焦磷酸基团的位置;这解释了β 1 β 1和β 2 β 2同工酶之间的功能差异，包括较低的最适pH值和较高的β 2 β 2转换数，这可能是突变形式。这种交换证明了在醇脱氢酶的进化中存在平行但独立的突变，因为这些哺乳动物酶在完全相同的位置上的不同之处在于在相应酵母酶的突变体和野生型组成型之间发现的相同类型的取代。
The homodimeric Oriental beta 2 beta 2 isozyme of human liver alcohol dehydrogenase, corresponding to an allelic variant at the ADH2 gene locus, was studied in order to define the amino acid exchange in relation to the beta 1 beta 1 isozyme, the predominant allelic form among Caucasians. Sequence analysis reveals that the amino acid substitution occurs at position 7 of the largest CNBr fragment, corresponding to position 47 of the whole protein chain. Here, the beta 2 form has a histidine residue, while, in common with other characterized mammalian liver alcohol dehydrogenases, the beta 1 form has an arginine residue. This exchange does not affect the adjacent cysteine-46 residue, which is a protein ligand to the active-site zinc atom, thus clarifying previously inconsistent results. The histidine/arginine-47 mutational replacement corresponds to a position that binds the pyrophosphate group of the coenzyme NAD(H); this explains the functional differences between the beta 1 beta 1 and beta 2 beta 2 isozymes, including both a lower pH optimum and higher turnover number of beta 2 beta 2, which is likely to be the mutant form. The exchange demonstrates the existence of parallel but separate mutations in the evolution of alcohol dehydrogenases because these mammalian enzymes differ at exactly the same position by the same type of substitution as is found between a mutant and the wild-type constitutive forms of the corresponding yeast enzyme.