Lee I Y, Chance B
Adv Exp Med Biol. 1977;85A:203-24. doi: 10.1007/978-1-4899-5181-6_14.
The factors affecting acetaldehyde oxidation were studied by direct measurement of redox changes of NADH and cytochrome c in isolated rat liver mitochondria which contain the natural complement of mitochondrial substrates and co-factors, etc. Thus, this system affords a quantitative model for mitochondrial acetaldehyde metabolism simulating in vivo conditions. The activity of acetaldehyde dehydrogenase, as measured by the turnover number of cytochrome c, k3, depends upon the substrate concentration in a complex way. It reaches a maximum below 0.033 mM acetaldehyde and decreases abruptly at higher acetaldehyde concentration, interpreted here to be due to substrate inhibition. When mitochondria undergo hypotonic swelling, the maximal value of k3 is lowered by a factor of 15 and the substrate inhibition largely disappears. When mitochondria are stripped of the outer membrane and are suspended in pyrophosphate buffer, similar effects are obtained. It is concluded that acetaldehyde oxidation in mitochondria is dependent upon the state of mitochondria and the substrate concentration, and that the mitochondrial metabolism of acetaldehyde cannot be accurately predicted from in vitro data of solubilized enzyme.
通过直接测量含有天然线粒体底物和辅助因子等的离体大鼠肝线粒体中NADH和细胞色素c的氧化还原变化，研究了影响乙醛氧化的因素。因此，该系统为模拟体内条件的线粒体乙醛代谢提供了一个定量模型。以细胞色素c的周转数k3衡量的乙醛脱氢酶活性，以复杂的方式依赖于底物浓度。在乙醛浓度低于0.033 mM时达到最大值，在较高乙醛浓度时急剧下降，在此解释为底物抑制所致。当线粒体发生低渗肿胀时，k3的最大值降低15倍，底物抑制作用基本消失。当线粒体去除外膜并悬浮在焦磷酸盐缓冲液中时，也会得到类似的效果。结论是线粒体中乙醛的氧化依赖于线粒体的状态和底物浓度，并且不能从溶解酶的体外数据准确预测乙醛的线粒体代谢。
