The stereochemical course of 4-hydroxy-2-nonenal metabolism by glutathione S-transferases
The stereochemical course of 4-hydroxy-2-nonenal metabolism by glutathione S-transferases
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DOI：
10.1074/jbc.m801725200
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发表时间：
2008-06-13
影响因子：
4.8
通讯作者：
Atkins, William M.
中科院分区：
文献类型：
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作者：
Balogh, Larissa M.;Roberts, Arthur G.;Atkins, William M.
4-羟基-2-壬烯醛（HNE）是脂质过氧化过程中产生的一种有毒醛，与氧化应激相关的多种病理状态有关。谷胱甘肽s -转移酶（GST） A4-4被认为是负责HNE代谢的主要酶之一。然而，底物和产物的立体选择性仍有待充分探索。产物形成分析结果表明，hGSTA4-4在两种对映体存在时表现出适度的S-HNE生物转化偏好。使用外消旋和对映异构体HNE底物的液相色谱质谱分析明确表明，hGSTA4-4以完全立体选择性的方式将谷胱甘肽与HNE对映异构体结合，而这种方式在自发反应中无法维持。与其他hGST异构体相比，hGSTA4-4具有最高的立体选择性。核磁共振实验与模拟退火结构测定相结合，可以确定GSHNE非对映体的立体化学构型，并且与hgsta4 -4催化的亲核攻击相一致，该攻击只在共轭位点产生s构型，而不考虑底物手性。总的来说，这些结果表明hGSTA4-4表现出低底物立体选择性和严格的产物立体选择性的有趣组合。这种行为允许两种HNE对映体的解毒，同时只产生一组选择的GSHNE非对映体，这些非对映体具有潜在的立体化学意义，涉及其在生物组织中的作用和命运。
4-Hydroxy-2-nonenal (HNE) is a toxic aldehyde generated during lipid peroxidation and has been implicated in a variety of pathological states associated with oxidative stress. Glutathione S-transferase (GST) A4-4 is recognized as one of the predominant enzymes responsible for the metabolism of HNE. However, substrate and product stereoselectivity remain to be fully explored. The results from a product formation assay indicate that hGSTA4-4 exhibits a modest preference for the biotransformation of S-HNE in the presence of both enantiomers. Liquid chromatography mass spectrometry analyses using the racemic and enantioisomeric HNE substrates explicitly demonstrate that hGSTA4-4 conjugates glutathione to both HNE enantiomers in a completely stereoselective manner that is not maintained in the spontaneous reaction. Compared with other hGST isoforms, hGSTA4-4 shows the highest degree of stereoselectivity. NMR experiments in combination with simulated annealing structure determinations enabled the determination of stereochemical configurations for the GSHNE diastereomers and are consistent with an hGSTA4-4-catalyzed nucleophilic attack that produces only the S-configuration at the site of conjugation, regardless of substrate chirality. In total these results indicate that hGSTA4-4 exhibits an intriguing combination of low substrate stereoselectivity with strict product stereoselectivity. This behavior allows for the detoxification of both HNE enantiomers while generating only a select set of GSHNE diastereomers with potential stereochemical implications concerning their effects and fates in biological tissues.