The mutation in the mitochondrial aldehyde dehydrogenase (ALDH2) gene responsible for alcohol-induced flushing increases turnover of the enzyme tetramers in a dominant fashion
The mutation in the mitochondrial aldehyde dehydrogenase (ALDH2) gene responsible for alcohol-induced flushing increases turnover of the enzyme tetramers in a dominant fashion
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DOI：
10.1172/jci119007
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发表时间：
1996-11-01
影响因子：
15.9
通讯作者：
Crabb, DW
中科院分区：
文献类型：
--
作者：
Xiao, Q;Weiner, H;Crabb, DW
线粒体乙醛脱氢酶 (ALDHZ)（一种四聚体酶）的缺陷是由遗传一个或两个 ALDH2*2 等位基因引起的。该等位基因编码一个蛋白质亚基，在第 487 位用赖氨酸取代谷氨酸，并且比野生型等位基因 ALDH2*1 占优势。 ALDH2*2 编码的亚基 (ALDH2K) 会降低表达野生型亚基 (ALDH2E) 的细胞系中 ALDH2 酶的活性。除了对酶活性的影响之外，我们现在报告说，尸检肝脏样本中 ALDH2*2 杂合子的 ALDH2 免疫反应蛋白水平较低。表达 ALDH2*1、ALDH2*2 或两者的 HeLa 细胞系中 ALDH2 蛋白的半衰期是通过用嘌呤霉素抑制蛋白质合成后免疫反应蛋白的丢失率和脉冲追踪实验来确定的。通过任一测量，ALDH2E 酶都非常稳定，半衰期至少为 22 小时，ALDH2K 酶的酶半衰期仅为 14 小时。在表达两个亚基的细胞中，大多数亚基组装为异四聚体，这些酶的半衰期为13小时，因此，ALDH2K对酶周转的影响占主导地位。这些研究表明 ALDH2*2 等位基因通过干扰酶的催化活性和增加其周转来发挥其主导作用。这是第一个显性作用等位基因对线粒体酶的周转产生影响的例子。
Deficiency in mitochondrial aldehyde dehydrogenase (ALDHZ), a tetrameric enzyme, results from inheriting one or two ALDH2*2 alleles, This allele encodes a protein subunit with a lysine for glutamate substitution at position 487 and is dominant over the wild-type allele, ALDH2*1. The ALDH2*2-encoded subunit (ALDH2K) reduces the activity of ALDH2 enzyme in cell lines expressing the wild-type subunit (ALDH2E). In addition to this effect on the enzyme activity, we now report that ALDH2*2 heterozygotes had lower levels of ALDH2 immunoreactive protein in autopsy liver samples. The half-lives of ALDH2 protein in HeLa cell lines expressing ALDH2*1, ALDH2*2, or both were determined by the rate of loss of immunoreactive protein after inhibition of protein synthesis with puromycin and by pulse-chase experiments, By either measure, ALDH2E enzyme was very stable, with a half-life of at least 22 h, ALDH2K enzyme had an enzyme half-life of only 14 h, In cells expressing both subunits, most of the subunits assemble as heterotetramers, and these enzymes had a half-life of 13 h, Thus, the effect of ALDH2K on enzyme turnover is dominant. These studies indicate that the ALDH2*2 allele exerts its dominant effect both by interfering with the catalytic activity of the enzyme and by increasing its turnover. This represents the first example of a dominantly acting allele with this effect on a mitochondrial enzyme's turnover.