Leão C, Van Uden N
Biochim Biophys Acta. 1984 Jul 11;774(1):43-8. doi: 10.1016/0005-2736(84)90272-4.
Ethanol, isopropanol, propanol and butanol enhanced the passive influx of protons into deenergized cells of Saccharomyces cerevisiae. The influx followed first-order kinetics with a rate constant that increased exponentially with the alkanol concentration. The exponential enhancement constants increased with the lipid solubility of the alkanols, which indicated hydrophobic membrane regions as the target sites. While the enhancement constants were independent of pH over the range tested (3.3-5.0), the rate constants decreased linearly with increasing extracellular proton concentration, indicating the presence of an additional surface barrier against proton penetration, the effectiveness of which increased with protonation. The alkanols affected the acidification curves of energized yeast suspensions in such a way that the final pH values were linear functions of the alkanol concentrations. These results were consistent with a balance between active and passive proton movements at the final pH, the exponential enhancement constants calculated from the slopes being nearly identical with those obtained with deenergized cells. It was concluded that passive proton influx contributes to the kinetics of acidification in S. cerevisiae and that uncoupling contributes to the overall kinetics of alkanol-inhibited secondary active transport across the yeast plasma membrane.
乙醇、异丙醇、丙醇和丁醇增强了质子向去能化的酿酒酵母细胞的被动内流。这种内流遵循一级动力学，其速率常数随链烷醇浓度呈指数增加。指数增强常数随链烷醇的脂溶性增加而增加，这表明疏水膜区域是靶位点。虽然增强常数在所测试的pH范围内（3.3 - 5.0）与pH无关，但速率常数随细胞外质子浓度的增加呈线性下降，这表明存在额外的质子渗透表面屏障，其有效性随质子化而增加。链烷醇以这样一种方式影响有能酵母悬浮液的酸化曲线，即最终pH值是链烷醇浓度的线性函数。这些结果与最终pH下主动和被动质子运动之间的平衡一致，从斜率计算得到的指数增强常数与用去能化细胞得到的几乎相同。得出的结论是，被动质子内流有助于酿酒酵母的酸化动力学，并且解偶联有助于链烷醇抑制的跨酵母质膜的次级主动转运的整体动力学。
