Effects of Ethanol and Other Alkanols on Transport of Acetic Acid in Saccharomyces cerevisiae
Effects of Ethanol and Other Alkanols on Transport of Acetic Acid in Saccharomyces cerevisiae
复制标题
乙醇和其他烷醇对酿酒酵母中乙酸转运的影响
DOI：
10.1128/aem.64.2.665-668.1998
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发表时间：
1998
影响因子：
4.4
通讯作者：
C. Leão
中科院分区：
文献类型：
--
作者：
M. Casal;H. Cardoso;C. Leão
在酿酒酵母IGC 4072的葡萄糖培养细胞中，醋酸仅通过未解离酸的简单扩散进入。在这些细胞中，乙醇和其他烷醇增强了标记乙酸的被动内流。酸的流入遵循一级动力学，其速率常数随醇浓度呈指数增长，并估计每种醇的指数增强常数。醇类也能提高标记乙酸的细胞内浓度，且随酒精浓度的增加呈指数增长。醋酸通过醋酸-质子对称转运穿过醋酸、乳酸和乙醇细胞的质膜。我们发现，在这些细胞中，乙醇和丁醇以非竞争性的方式抑制标记乙酸的运输；最大输运速度随醇浓度的增加而降低，而体系对乙酸酯的亲和力不受醇浓度的显著影响。Vmax与酒精浓度的半对数图产生负斜率的直线，由此可以估计每种醇的抑制常数。在乙醇或丁醇的存在下，细胞内标记酸的浓度显著降低，并随酒精浓度的增加而增加。我们推测，酿酒酵母在葡萄糖培养的细胞中缺乏醋酸的操作载体，再加上质膜对未解离酸的相对高的渗透性和生物体无法代谢乙酸，可能是该物种对含乙醇的酸性环境表现出低耐受性的原因之一。
ABSTRACT In glucose-grown cells of Saccharomyces cerevisiae IGC 4072, acetic acid enters only by simple diffusion of the undissociated acid. In these cells, ethanol and other alkanols enhanced the passive influx of labelled acetic acid. The influx of the acid followed first-order kinetics with a rate constant that increased exponentially with the alcohol concentration, and an exponential enhancement constant for each alkanol was estimated. The intracellular concentration of labelled acetic acid was also enhanced by alkanols, and the effect increased exponentially with alcohol concentration. Acetic acid is transported across the plasma membrane of acetic acid-, lactic acid-, and ethanol-grown cells by acetate-proton symports. We found that in these cells ethanol and butanol inhibited the transport of labelled acetic acid in a noncompetitive way; the maximum transport velocity decreased with alcohol concentration, while the affinity of the system for acetate was not significantly affected by the alcohol. Semilog plots of Vmax versus alcohol concentration yielded straight lines with negative slopes from which estimates of the inhibition constant for each alkanol could be obtained. The intracellular concentration of labelled acid was significantly reduced in the presence of ethanol or butanol, and the effect increased with the alcohol concentration. We postulate that the absence of an operational carrier for acetate in glucose-grown cells of S. cerevisiae, combined with the relatively high permeability of the plasma membrane for the undissociated acid and the inability of the organism to metabolize acetic acid, could be one of the reasons why this species exhibits low tolerance to acidic environments containing ethanol.