ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Life and Medical Sciences  (4)
  • sugar metabolism  (3)
  • mitochondria
  • 1995-1999  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Physiological characterisation of a pyruvate-carboxylase-negative Saccharomyces cerevisiae mutant in batch and chemostat cultures (1998)
    Springer
    Antonie van Leeuwenhoek 74 (1998), S. 253-263 
    Details
    ISSN: 1572-9699
    Keywords: Saccharomyces cerevisiae ; pyruvate carboxylase ; anaplerotic reactions ; sugar metabolism ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A prototrophic pyruvate-carboxylase-negative (Pyc-) mutant was constructed by deleting the PYC1 and PYC2 genes in a CEN.PK strain of Saccharomyces cerevisiae. Its maximum specific growth rate on ethanol was identical to that of the isogenic wild type but it was unable to grow in batch cultures in glucose-ammonia media. Consistent with earlier reports, growth on glucose could be restored by supplying aspartate as a sole nitrogen source. Ethanol could not replace aspartate as a source of oxaloacetate in batch cultures. To investigate whether alleviation of glucose repression allowed expression of alternative pathways for oxaloacetate synthesis, the Pyc- strain and an isogenic wild-type strain were grown in aerobic carbon-limited chemostat cultures at a dilution rate of 0.10 h-1 on mixtures of glucose and ethanol. In such mixed-substrate chemostat cultures of the Pyc- strain, steady-state growth could only be obtained when ethanol contributed 30% or more of the substrate carbon in the feed. Attempts to further decrease the ethanol content of the feed invariably resulted in washout. In Pyc- as well as in wild-type cultures, levels of isocitrate lyase, malate synthase and phospho-enol-pyruvate carboxykinase in cell extracts decreased with a decreasing ethanol content in the feed. Nevertheless, at the lowest ethanol fraction that supported growth of the Pyc- mutant, activities of the glyoxylate cycle enzymes in cell extracts were still sufficient to meet the requirement for C4-compounds in biomass synthesis. This suggests that factors other than glucose repression of alternative routes for oxaloacetate synthesis prevent growth of Pyc-mutants on glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001772613615
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Regulation of carbon metabolism in chemostat cultures of Saccharomyces cerevisiae grown on mixtures of glucose and ethanol (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 11 (1995), S. 407-418 
    Details
    ISSN: 0749-503X
    Keywords: chemostat ; mixed substrates ; gluconeogenesis ; glyoxylate cycle ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Growth efficiency and regulation of key enzyme activities were studied in carbon- and energy-limited chemostat cultures of Saccharomyces cerevisiae grown on mixtures of glucose and ethanol at a fixed dilution rate. Biomass yields on substrate carbon and oxygen could be adequately described as the net result of growth on the single substrates. Activities of isocitrate lyase and malate synthase were not detected in cell-free extracts of glucose-limited cultures. However, both enzymes were present when the ethanol fraction in the reservoir medium exceeded the theoretical minimum above which the glyoxylate cycle is required for anabolic reactions. Fructose-1,6-bisphosphatase activity was only detectable at high ethanol fractions in the feed, when activity of this enzyme was required for synthesis of hexose phosphates. Phospho-enol-pyruvate-carboxykinase activity was not detectable in extracts from glucose-grown cultures and increased with the ethanol fraction in the feed. It is concluded that, during carbon-limited growth of S. cerevisiae on mixtures of glucose and ethanol, biosynthetic intermediates with three or more carbon atoms are preferentially synthesized from glucose. Synthesis of the key enzymes of gluconeogenesis and the glyoxylate cycle is adapted to the cells′ requirement for these intermediates. The gluconeogenic enzymes and their physiological antagonists (pyruvate kinase, pyruvate carboxylase and phosphofructokinase) were expressed simultaneously at high ethanol fractions in the feed. If futile cycling is prevented under these conditions, this is not primarily achieved by tight control of enzyme synthesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320110503
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Regulation of alcoholic fermentation in batch and chemostat cultures of Kluyveromyces lactis CBS 2359 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 14 (1998), S. 459-469 
    Details
    ISSN: 0749-503X
    Keywords: Crabtree effect ; yeast ; biomass ; Kluyveromyces lactis ; oxygen ; pyruvate decarboxylase ; regulation ; fermentation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Kluyveromyces lactis is an important industrial yeast, as well as a popular laboratory model. There is currently no consensus in the literature on the physiology of this yeast, in particular with respect to aerobic alcoholic fermentation (‘Crabtree effect’). This study deals with regulation of alcoholic fermentation in K. lactis CBS 2359, a proposed reference strain for molecular studies. In aerobic, glucose-limited chemostat cultures (D=0·05-0·40 h-1) growth was entirely respiratory, without significant accumulation of ethanol or other metabolites. Alcoholic fermentation occurred in glucose-grown shake-flask cultures, but was absent during batch cultivation on glucose in fermenters under strictly aerobic conditions. This indicated that ethanol formation in the shake-flask cultures resulted from oxygen limitation. Indeed, when the oxygen feed to steady-state chemostat cultures (D=0·10 h-1) was lowered, a mixed respirofermentative metabolism only occurred at very low dissolved oxygen concentrations (less than 1% of air saturation). The onset of respirofermentative metabolism as a result of oxygen limitation was accompanied by an increase of the levels of pyruvate decarboxylase and alcohol dehydrogenase. When aerobic, glucose-limited chemostat cultures (D=0·10 h-1) were pulsed with excess glucose, ethanol production did not occur during the first 40 min after the pulse. However, a slow aerobic ethanol formation was invariably observed after this period. Since alcoholic fermentation did not occur in aerobic batch cultures this is probably a transient response, caused by an imbalanced adjustment of enzyme levels during the transition from steady-state growth at μ=0·10 h-1 to growth at μmax. It is concluded that in K. lactis, as in other Crabtree-negative yeasts, the primary environmental trigger for occurrence of alcoholic fermentation is oxygen limitation. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Pyruvate Metabolism in Saccharomyces cerevisiae (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 1607-1633 
    Details
    ISSN: 0749-503X
    Keywords: Yeast ; glycolysis ; TCA cycle ; sugar metabolism ; metabolic engineering ; pyruvate decarboxylase ; pyruvate carboxylase ; pyruvate dehydrogenase complex ; alcoholic fermentation ; Crabtree effect ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In yeasts, pyruvate is located at a major junction of assimilatory and dissimilatory reactions as well as at the branch-point between respiratory dissimilation of sugars and alcoholic fermentation. This review deals with the enzymology, physiological function and regulation of three key reactions occurring at the pyruvate branch-point in the yeast Saccharomyces cerevisiae: (i) the direct oxidative decarboxylation of pyruvate to acetyl-CoA, catalysed by the pyruvate dehydrogenase complex, (ii) decarboxylation of pyruvate to acetaldehyde, catalysed by pyruvate decarboxylase, and (iii) the anaplerotic carboxylation of pyruvate to oxaloacetate, catalysed by pyruvate carboxylase. Special attention is devoted to physiological studies on S. cerevisiae strains in which structural genes encoding these key enzymes have been inactivated by gene disruption.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Transient responses of Candida utilis to oxygen limitation: Regulation of the Kluyver effect for maltose (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 11 (1995), S. 317-325 
    Details
    ISSN: 0749-503X
    Keywords: yeast ; Candida utilis ; alcoholic fermentation ; Kluyver effect ; oxygen limitation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: 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.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320110404
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Pyruvate decarboxylase: An indispensable enzyme for growth of Saccharomyces cerevisiae on glucose (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 247-257 
    Details
    ISSN: 0749-503X
    Keywords: pyruvate decarboxylase ; sugar metabolism ; Saccharomyces cerevisiae ; metabolic compartmentation ; acetyl-CoA ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In Saccharomyces cerevisiae, the structural genes PDC1, PDC5 and PDC6 each encode an active pyruvate decarboxylase. Replacement mutations in these genes were introduced in a homothallic wild-type strain, using the dominant marker genes APT1 and Tn5ble. A pyruvate-decarboxylase-negative (Pdc-) mutant lacking all three PDC genes exhibited a three-fold lower growth rate in complex medium with glucose than the isogenic wild-type strain. Growth in batch cultures on complex and defined media with ethanol was not impaired in Pdc- strains. Furthermore, in ethanol-limited chemostat cultures, the biomass yield of Pdc- and wild-type S. cerevisiae were identical. However, Pdc- S. cerevisiae was unable to grow in batch cultures on a defined mineral medium with glucose as the sole carbon source. When aerobic, ethanol-limited chemostat cultures (D = 0·10 h-1) were switched to a feed containing glucose as the sole carbon source, growth ceased after approximately 4 h and, consequently, the cultures washed out. The mutant was, however, able to grow in chemostat cultures on mixtures of glucose and small amounts of ethanol or acetate (5% on a carbon basis). No growth was observed when such cultures were used to inoculate batch cultures on glucose. Furthermore, when the mixed-substrate cultures were switched to a feed containing glucose as the sole carbon source, wash-out occurred. It is concluded that the mitochondrial pyruvate dehydrogenase complex cannot function as the sole source of acetyl-CoA during growth of S. cerevisiae on glucose, neither in batch cultures nor in glucose-limited chemostat cultures.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...