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  • 1
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Baker's yeast (Saccharomyces cerevisiae) was cultivated under different intensities of aeration on glucose and on ethanol. Seventeen enzymes of the Embden-Meyerhof pathway and the TCA cycle or related reactions were then assayed by starch gel electrophoresis. There were both qualitative and quantitative differences in many enzymes, most notably in glyceraldehyde-3-phosphate dehydrogenase, alcohol dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase, and fumarase. Enzyme electrophoresis seems to offer a promising method for rapidly obtaining information about many yeast enzymes from a large number of samples.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. It has been confirmed that under anaerobic conditions at pH 2 pyruvic acid is vigorously decarboxylated by intact baker's yeast, but hardly at all at pH 5.5. Furthermore, the decarboxylation occurs more slowly with semiaerobically cultured than with aerobically cultured baker's yeast. 2. The penetration of pyruvic acid ethyl ester into the cell is not dependent upon the pH of the medium. The ester is decarboxylated by intact yeast at about the same rate, at pH 2 and 5.5. It is not decarboxylated by a purified preparation of pyruvate decarboxylase (EC 4.1.1.1). 3. Hydroxypyruvic acid is decarboxylated only slowly by intact yeast at pH 2 and pyruvate decarboxylase. The attachment of a phenyl group to the pyruvic acid molecule increase the permeability, but causes an inhibition of pyruvate decarboxylase. 4. α-Ketoglutaric acid is decarboxylated neither by intact yeast nor by an enzyme preparation, but with disintegrated yeast a noticeable formation of CO2 is observable. By intact yeast, the γ-ethyl ester of α-ketoglutaric acid reacts towards the acidity of the medium in the same way as does pyruvic acid. With purified pyruvate decarboxylase, the ester is decarboxylated more slowly than α-ketovaleric acid, but more rapidly than α-ketocaproic acid. Nevertheless, it does not penetrate into the intact yeast cell at a weak concentration to the same extent as do the acids last mentioned. α-Ketoglutaric acid diethyl ester behaves in a similar way to pyruvic acid ethyl ester: it penetrates the plasma membrane, and is decarboxylated by yeast but not by a preparation of pyruvate decarboxylase.
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  • 3
    ISSN: 1432-072X
    Keywords: Yeast ; Baker's yeast ; Biotin ; Biotinyl enzymes ; Pyruvate carboxylase ; Acetyl-CoA carboxylase ; Ureaamidolyase ; Pyruvate apocarboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The holo- and apocarboxylase proteins in baker's yeast grown in a chemostat at different biotin concentrations (from 0.1–200 μg/l) and on different carbon sources were assayed. The growth and the type of metabolism are considered with respect to the activity of the enzymes involved in oxaloacetate regeneration (pyruvate carboxylase and isocitrate lyase activities). In order to assay the level of apocarboxylase protein in the cells the characteristics of the pyruvate holocarboxylase formation in permeabilized cells were studied and thereby an assay method was developed. The pyruvate carboxylase activity of the cells grown in a medium with 4% glucose as the carbon source was almost constant from the lowest biotin concentration up to a biotin concentration of 10 μg/l, after which it rose and obtained a maximum at a biotin concentration of about 50 μg/l. The content of the apocarboxylase protein was maximal at 0.5 μg/l biotin, and then exceeded the level of the active pyruvate carboxylase protein by a factor of about 2.5. With increasing biotin concentration in the medium the content of apocarboxylase protein decreased and was negligible in cells grown at biotin concentrations higher than 100 μg/l. The total content of pyruvate carboxylase protein (i.e. apo- + holoenzyme) was roughly constant over a wide biotin concentration range (from 0.5–15 μg/l), the maximum being only double the minimum. At a biotin concentration 50 μg/l, where the maximum yield was reached, the cells still contained pyruvate apocarboxylase. The rapid increase in yield found around a biotin concentration of 10 μg/l correlates, on the basis of measured enzyme activities, more with the appearance of activity of glyoxylate cycle enzymes than with the increase in the activity of pyruvate carboxylase. When cells were growing on ethanol with biotin as the growth limiting factor, the cells still used biotin for the formation of pyruvate holocarboxylase, and proportionally more of the total content of pyruvate carboxylase protein was in the form of holoenzyme than in the cells growing on glucose under biotin limitation. The existence of urea amidolyase apoprotein in yeast cells grown with urea as the sole nitrogen source under biotin deficiency is reported. The presence of acetyl-CoA apocarboxylase in biotin-deficient cells could not be demonstrated.
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  • 4
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; Baker's yeast ; Gluconeogenetic enzymes ; Chemostat ; Oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The effect of aeration on the key enzymes of gluconeogenesis was studied in baker's yeast (Saccharomyces cerevisiae) and in a nonrespiratory variant of S. cerevisiae grown under glucose limitation. 2. In baker's yeast phosphoenolpyruvate carboxykinase, hexosediphosphatase and isocitrate lyase were completely repressed under anaerobic conditions. Their repression could be partially reversed by using intense aeration. 3. In the nonrespiratory variant these enzymes were absent independently of aeration. 4. Pyruvate carboxylase of baker's yeast showed maximal activity under anaerobic conditions. In the nonrespiratory variant pyruvate carboxylase had low activity under both anaerobic and aerobic conditions.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 12 (1959), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Efforts were made to eliminate the influence of other factors as far as possible in order to obtain reliable results on the effects of oxygen on the growth of baker's yeast. A cultivation method is presented which permits the study of the effects of aeration intensity under conditions where the influence of catabolite repression is eliminated. A completely synthetic medium with glucose as the only carbon and energy source is also described.The capacity of yeast to perform aerobic metabolism varies when cultivated under different intensities of aeration. A clear maximum is observed for growth with 10% oxygen in the aerating gas mixture. Under conditions where catabolite repression does not function yeast has the potential for oxidative metabolism even under oxygen-limited growth. The main agent controlling the ability of yeast to support growth using only the oxidative metabolism is the available oxygen.At high oxygen tensions the metabolism is disturbed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 16 (1974), S. 1213-1225 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When the effect of catabolite repression is eliminated Saccharomyces cerevisiae prefers an aerobic metabolism. The potential for completely aerobic catabolism exists even in circumstances where its action is limited by the oxygen available. When the oxygen absorption in the medium is adequate, yeast uses a solely oxidative metabolism for energy-yielding reactions. The changes observed in the activity of malate dehydrogenase can be described as a function of two isoenzymes, both of which are affected by oxygen; the isoenzyme participating in the glyoxylate cycle shows variations in activity similar to that observed in isocitrate lyase. NAD-linked glutamate dehydrogenase activity roughly follows that of malate dehydrogenase and isocitrate lyase; in cultivations with the same growth rate the NADP-linked dehydrogenase is insensitive to the oxygen level. The cytochromes aa3, b, and c have a clear maximum at low oxygen tension, the most sensitive being cytochrome aa3. The imbalance between cytochrome c:oxygen oxidoreductase activity and the amount of cytochrome aa3, and the correlation observed between respiration rate and the activities of cytochrome c oxidase and NADH2:cytochroine c oxidoreductase are discussed. Methods used for estimation of cytochromes are compared.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A series of baker's yeast continuous cultivations were made using different intensities of aeration. The experimental conditions were such as to eliminate the effects caused by high glucose concentrations in the medium on the formation of enzymes. The variation in activity of several enzymes was investigated and distinct changes were noted. The activities of hexokinase and alcohol dehydrogenase characterize the actual rate of glycolysis in yeast, the same being true, in part, for pyruvate decarboxylase. The activity of phosphofructokinase is nearly insensitive to the oxygen level at normal tensions. The activity of the cell to the phosphofructokinase can be limited in anaerobic conditions by its scarcity. The insensitivity of glucose-6-phosphate dehydrogenase to the oxygen tension together with its low activity suggests that this enzyme plays primarily a biosynthetic role and that the function of the pentose phosphate pathway as an energy-producing route is negligible.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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