Regulation of primary carbon metabolism in Kluyveromyces lactis

In the recent past, through advances in development of genetic tools, the b udding yeast Kluyveromyces lactis has become a model system for studies on molecular physiology of so-called "Nonconventional Yeasts." The regulation of primary carbon metabolism in K. lactis differs markedly from Saccharomyc es cerevisiae and reflects the dominance of respiration over fermentation t ypical for the majority of yeasts. The absence of aerobic ethanol formation in this class of yeasts represents a major advantage for the "cell factory " concept and large-scale production of heterologous proteins in K. lactis cells is being applied successfully. First insight into the molecular basis for the different regulatory strategies is beginning to emerge from compar ative studies on S. cerevisiae and K. lactis. The absence of glucose repres sion of respiration, a high capacity of respiratory enzymes and a tight reg ulation of glucose uptake in K. lactis are key factors determining physiolo gical differences to S, cerevisiae, A striking discrepancy exists between t he conservation of regulatory factors and the lack of evidence for their fu nctional significance in K. lactis. On the other hand, structurally conserv ed factors were identified in L. lactis in a new regulatory context. It see ms that different physiological responses result from modified interactions of similar molecular modules. (C) 2000 Elsevier Science Inc. All rights re served.