Ethanol and lactate are typical waste products of glucose fermentation. In mammals, glucose is catabolized by glycolysis into circulating lactate, which is broadly used throughout the body as a carbohydrate fuel. Individual cells can both uptake and excrete lactate, uncoupling glycolysis from glucose oxidation. Here we show that similar uncoupling occurs in budding yeast batch cultures of Saccharomyces cerevisiae and Issatchenkia orientalis. Even in fermenting S. cerevisiae that is net releasing ethanol, media ¹³C-ethanol rapidly enters and is oxidized to acetaldehyde and acetyl-CoA. This is evident in exogenous ethanol being a major source of both cytosolic and mitochondrial acetyl units. ²H-tracing reveals that ethanol is also a major source of both NADH and NADPH high-energy electrons, and this role is augmented under oxidative stress conditions. Thus, uncoupling of glycolysis from the oxidation of glucose-derived carbon via rapidly reversible reactions is a conserved feature of eukaryotic metabolism.

乙醇和乳酸是葡萄糖发酵的典型废物。在哺乳动物中，葡萄糖通过糖酵解分解代谢为循环乳酸，后者广泛用作全身的碳水化合物燃料。单个细胞可以摄取和排泄乳酸，将糖酵解与葡萄糖氧化解偶联。在这里，我们表明类似的解偶联发生在酿酒酵母和东方伊萨酵母的出芽酵母分批培养物中。即使在净释放乙醇的发酵酿酒酵母中，培养基¹³ C-乙醇也会迅速进入并氧化成乙醛和乙酰辅酶 A。这在外源性乙醇是细胞溶质和线粒体乙酰基单位的主要来源中是显而易见的。^2个H-示踪显示乙醇也是 NADH 和 NADPH 高能电子的主要来源，并且这种作用在氧化应激条件下得到增强。因此，通过快速可逆反应将糖酵解与葡萄糖衍生碳的氧化解偶联是真核代谢的一个保守特征。