Kaliterna J, Weusthuis R A, Castrillo J I, Van Dijken J P, Pronk J T
Department of Microbiology and Enzymology, Kluyer Laboratory of Biotechnology, Delft University of Technology, The Netherlands.
Yeast. 1995 Apr 15;11(4):317-25. doi: 10.1002/yea.320110404.
The facultatively fermentative yeast Candida utilis exhibits the Kluyver effect for maltose: this disaccharide is respired and assimilated but, in contrast to glucose, it cannot be fermented. To study the mechanism of the Kluyver effect, metabolic responses of C. utilis to a transition from aerobic, sugar-limited growth to oxygen-limited conditions were studied in chemostat cultures. Unexpectedly, the initial response of maltose-grown cultures to oxygen limitation was very similar to that of glucose-grown cultures. In both cases, alcoholic fermentation occurred after a lag phase of 1 h, during which glycerol, pyruvate and D-lactate were the main fermentation products. After ca. 10 h the behaviour of the maltose- and glucose-grown cultures diverged: ethanol disappeared from the maltose-grown cultures, whereas fermentation continued in steady-state, oxygen-limited cultures grown on glucose. The disappearance of alcoholic fermentation in oxygen-limited chemostat cultures growing on maltose was not due to a repression of the synthesis of pyruvate decarboxylase and alcohol dehydrogenase. The results demonstrate that the Kluyver effect for maltose in C. utilis does not reflect an intrinsic inability of this yeast to ferment maltose, but is caused by a regulatory phenomenon that affects a key enzyme in maltose metabolism, probably the maltose carrier. The observed kinetics indicate that this regulation occurs at the level of enzyme synthesis rather than via modification of existing enzyme activity.
这种二糖可被呼吸和同化，但与葡萄糖不同，它不能被发酵。为了研究克鲁维效应的机制，在恒化器培养中研究了产朊假丝酵母从需氧、糖限制生长转变为氧限制条件下的代谢反应。出乎意料的是，麦芽糖培养物对氧限制的初始反应与葡萄糖培养物非常相似。在这两种情况下，酒精发酵在1小时的延迟期后发生，在此期间甘油、丙酮酸和D-乳酸是主要的发酵产物。大约10小时后，麦芽糖培养物和葡萄糖培养物的行为出现分歧：麦芽糖培养物中的乙醇消失，而在以葡萄糖为碳源的稳态氧限制培养物中发酵继续进行。在以麦芽糖为碳源的氧限制恒化器培养物中酒精发酵的消失不是由于丙酮酸脱羧酶和乙醇脱氢酶合成的抑制。结果表明，产朊假丝酵母对麦芽糖的克鲁维效应并不反映该酵母发酵麦芽糖的内在无能，而是由一种调节现象引起的，这种调节现象影响麦芽糖代谢中的一种关键酶，可能是麦芽糖载体。观察到的动力学表明，这种调节发生在酶合成水平，而不是通过对现有酶活性的修饰。
