Ethanol formation and enzyme activities around glucose-6-phosphate in Kluyveromyces marxianus CBS 6556 exposed to glucose or lactose excess
Ethanol formation and enzyme activities around glucose-6-phosphate in Kluyveromyces marxianus CBS 6556 exposed to glucose or lactose excess
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DOI：
10.1016/j.femsyr.2004.01.004
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发表时间：
2004-05-01
影响因子：
3.2
通讯作者：
Gombert, AK
中科院分区：
文献类型：
--
作者：
Bellaver, LH;de Carvalho, NMB;Gombert, AK
本研究的目的是研究马氏克卢维菌CBS 6556在过量糖暴露下形成乙醇的低倾向，以及在葡萄糖-6-磷酸水平上发生的碳通量的分裂。测量是在批量培养中进行的，并且在将葡萄糖或乳糖脉冲应用于恒化剂生长的呼吸细胞（稀释率为0.1 h(-1)）之后进行的。在批量培养或脉冲实验中没有观察到乙醇的形成，除非氧气供应被关闭，这表明该生物比其近亲K乳酸和其他已知的crabtree阴性酵母更严格地呈阴性。在脉冲实验过程中，无细胞提取物的磷酸糖异构酶、葡萄糖-6-磷酸脱氢酶和磷酸糖脲酶活性基本保持不变，高于同等条件下培养的酿酒酵母。当细胞暴露于葡萄糖浓度高达26 gl（-1）时，磷酸葡萄糖糖化酶的活性高于暴露于14 gl（-1）的细胞，而磷酸葡萄糖异构酶和葡萄糖-6-磷酸脱氢酶的活性没有变化。我们的研究结果表明，马氏酵母中乙醇形成的低趋势可能是这种酵母保持糖酵解通量恒定的能力的结果，至少部分原因是碳通量转向了碳水化合物的生物合成和戊糖磷酸途径。(C) 2004年欧洲微生物学会联合会。Elsevier B.V.版权所有。
The aim of this work was to investigate the physiology of Kluyveromyces marxianus CBS 6556 in terms of its low tendency to form ethanol under exposure to sugar excess, and the split of carbon flux which takes place at the level of glucose-6-phosphate. Measurements were performed in batch cultivations, and after a glucose or a lactose pulse applied to chemostat-grown respiring cells (with a dilution rate of 0.1 h(-1)). No ethanol formation was observed in batch cultivations or during pulse experiments, unless the oxygen supply was shut down, indicating that this organism is more strictly Crabtree-negative than its close relative K lactis and other known Crabtree-negative yeasts. During the pulse experiments, activities of phosphoglucoisomerase, glucose-6-phosphate dehydrogenase and phosphoglucomutase in cell-free extracts remained rather constant, at higher levels than those of Saccharomyces cerevisiae grown at similar conditions. When cells were exposed to glucose concentrations as high as 26 gl(-1), the activity of phosphoglucomutase was higher than that in cells exposed to 14 gl(-1) glucose, whereas the activities of phosphoglucoisomerase and glucose-6-phosphate dehydrogenase did not change. Our results suggest that the low tendency for ethanol formation in K. marxianus might be a consequence of this yeast's capacity of keeping the glycolytic flux constant, due at least in part to the diversion of carbon flux towards the biosynthesis of carbohydrates and towards the pentose phosphate pathway. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.