人肝线粒体醛脱氢酶:三维结构和嵌合形式的溶解度和活性的恢复。
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倪琳，周杰，赫利，魏纳
人肝线粒体醛脱氢酶:三维结构和嵌合形式的溶解度和活性的恢复。
中国生物医学工程学报，1999,12(4):344 - 344。
- PubMed ID
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10631996 (PubMed视图］
- 摘要
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人肝中乙醛脱氢酶的胞浆同工酶和线粒体同工酶序列具有70%的同源性。然而，前21个残基在人类同工酶之间不保守(同源性15%)。牛肉线粒体和绵羊细胞质形态的三维结构具有几乎相同的三维结构。在这里，我们解决了人类线粒体酶的结构，发现它与牛肉酶完全相同。前21个残基位于酶的表面，不与四聚体中的其他亚基接触。在人类同工酶之间产生了一对嵌合酶。每个嵌合体的前21个残基来自一种同工酶，其余479个残基来自另一种同工酶。当前21个残基来自线粒体同工酶时，产生了一种具有细胞质样性质的酶。另一种表达了，但不溶。通过对n端残基进行点突变，可以恢复前21个细胞质残基与线粒体残基融合的嵌合体的溶解度和活性。 When residue 19 was changed from tyrosine to a cysteine, the residue found in the mitochondrial form, an active enzyme could be made though the Km for NAD+ was 35 times higher than the native mitochondrial isozyme and the specific activity was reduced by 75%. This residue interacts with residue 203, a nonconserved, nonactive site residue. A mutation of residue 18, which also interacts with 203, restored solubility, but not activity. Mutation to residue 15, which interacts with 104, also restored solubility but not activity. It appears that to have a soluble or active enzyme a favorable interaction must occur between a residue in a surface loop and a residue elsewhere in the molecule even though neither make contact with the active site region of the enzyme.