Phosphoketolase in Rhodotorula graminis and Other Yeasts

Whitworth, D. A.; Ratledge, Colin

doi:10.1099/00221287-102-2-397

Cited by 28 publications

(8 citation statements)

References 17 publications

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“…xylinum (26,29), Bifidobacterium bifidum (4), and Bifidobacterium globosum (30), whereas separate xylulose 5-phosphate and fructose 6-phosphate phosphoketolases have been described for L. mesenteroides (12), Bifidobacterium dentium (30), L. plantarum (10), Thiobacillus novellus (9), and various yeast species (5,34).…”

Section: Discussionmentioning

confidence: 99%

Pathway and regulation of erythritol formation in Leuconostoc oenos

1993

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It was recently observed that Leuconostoc oenos GM, a wine lactic acid bacterium, produced erythritol anaerobically from glucose but not from fructose or ribose and that this production was almost absent in the presence of O2. In this study, the pathway of formation of erythritol from glucose in L. oenos was shown to involve the isomerization of glucose 6-phosphate to fructose 6-phosphate by a phosphoglucose isomerase, the cleavage of fructose 6-phosphate by a phosphoketolase, the reduction of erythrose 4-phosphate by an erythritol 4-phosphate dehydrogenase and, finally, the hydrolysis of erythritol 4-phosphate to erythritol by a phosphatase. Fructose 6-phosphate phosphoketolase was copurified with xylulose 5-phosphate phosphoketolase, and the activity of the latter was competitively inhibited by fructose 6-phosphate, with a Ki of 26 mM, corresponding to the Km of fructose 6-phosphate phosphoketolase (22 mM). These results suggest that the two phosphoketolase activities are borne by a single enzyme. Extracts of L. oenos were also found to contain NAD(P)H oxidase, which must be largely responsible for the reoxidation of NADPH and NADH in cells incubated in the presence of O2. In cells incubated with glucose, the concentrations of glucose 6-phosphate and of fructose 6-phosphate were higher in the absence of O2 than in its presence, explaining the stimulation by anaerobiosis of erythritol production. The increase in the hexose 6-phosphate concentration is presumably the result of a functional inhibition of glucose 6-phosphate dehydrogenase because of a reduction in the availability of NADP.

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Section: Discussionmentioning

confidence: 99%

Pathway and regulation of erythritol formation in Leuconostoc oenos

1993

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“…Significance of the ratio of carbon source to the nitrogen source has been presented in studies of the lipid accumulation by microorgansims (3,4,11,12).…”

Section: Discussionmentioning

confidence: 99%

Physiological factors affecting total cell number and lipid content of the yeast, Lipomyces starkeyi.

Naganuma

Uzuka

Tanaka

1985

J. Gen. Appl. Microbiol.

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The effects of the concentration of the medium components and other cultural conditions on the total cell number and on the lipid content (mg of total lipid/108 cells) of the fat yeast Lipomyces starkeyi were examined. The no addition and deficiency of NH4+, K+, Mgt, P043-, SO42-, Zn2+, Fe3+, or Mn2+ decreased the total cell number. Mn2+ sufficiency increased the total cell number by a factor of 1.5 to 1.7, as compared with that of the standard concentration. The lipid content of the yeast was affected by six (NH4+, K+, Cat +, Zn2+, Fe3+, and Mn2+) ion concentrations. The no addition and deficiency of Zn2+ increased the lipid content by a factor ranging from 2.4 to 2.8 in comparison with that of the standard concentration. The concentration of Zn2+ also altered the lipid yield (g of lipid/100 g of glucose consumed) considerably. The concentration of Nat, Cl-, Cue, B033-, I-, Mo042-, and biotin had almost no effect on the total cell number, lipid content, and lipid yield of L. starkeyi. The cultural temperature and the initial pH value of the medium affected the total cell number and lipid content; the optimum temperature ranged from 25.5 to 29.5°C, and the optimum pH value was 4.9. A low concentration of dissolved oxygen decreased both the total cell number and lipid content. D-Glucose, D-mannose, D-galactose, Dlevulose, sucrose, D-xylose, and L-arabinose proved to be usable carbon sources for the growth and the lipid accumulation of L. starkeyi.Some yeasts accumulate a large amount of lipid in the cells. Although studies on lipid accumulation of microorganisms have been conducted since 1878, few reports on the physiological factors of lipid accumulation of yeasts have been published (1-4). The previous research conducted at our laboratory suggested that only a few trace elements affect the growth and the intracellular lipid (mainly 29

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“…However, two different pathways can be envisaged: 1) via transketolasel transaldolase, which results in formation of GAP, but in which carbon is lost via decarboxylation in the HMP pathway and 2) via phosphoketolase, which results in formation of GAP and acetylphosphate. A low phosphoketolase activity has been found in some yeasts (Whitworth & Ratledge 1977). The relative contribution of the three different routes to xylose metabolism is not known.…”

Section: Weak Acidsmentioning

confidence: 99%

Physiology of yeasts in relation to biomass yields

Verduyn¹

1992

Quantitative Aspects of Growth and Metabolism of Microorganisms

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The stoichiometric limit to the biomass yield (maximal assimilation of the carbon source) is determined by the amount of CO 2 lost in anabolism and the amount of carbon source required for generation of NADPH. This stoichiometric limit may be reached when yeasts utilize formate as an additional energy source. Factors affecting the biomass yield on single substrates are discussed under the following headings: -Energy requirement for biomass formation (YATP)' YATP depends strongly on the nature of the carbon source. Cell composition. The macroscopic composition of the biomass, and in particular the protein content, has a considerable effect on the ATP requirement for biomass formation. Hence, determination of for instance the protein content of biomass is relevant in studies on bioenergetics. Transport of the carbon source. Active (i.e. energy-requiring) transport, which occurs for a number of sugars and polyols, may contribute significantly to the calculated theoretical ATP requirement for biomass formation. Pia-ratio. The efficiency of mitochondrial energy generation has a strong effect on the cell yield. The Pia-ratio is determined to a major extent by the number of proton-translocating sites in the mitochondrial respiratory chain. Maintenance and environmental factors. Factors such as osmotic stress, heavy metals, oxygen and carbon dioxide pressures, temperature and pH affect the yield of yeasts. Various mechanisms may be involved, often affecting the maintenance energy requirement. Metabolites such as ethanol and weak acids. Ethanol increases the permeability ofthe plasma membrane, whereas weak acids can act as proton conductors. Energy content of the growth substrate. It has often been attempted in the literature to predict the biomass yield by correlating the energy content of the carbon source (represented by the degree of reduction) to the biomass yield or the percentage assimilation of the carbon source. An analysis of biomass yields of Candida uti/is on a large number of carbon sources indicates that the biomass yield is mainly determined by the biochemical pathways leading to biomass formation, rather than by the energy content of the substrate.

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Phosphoketolase in Rhodotorula graminis and Other Yeasts

Cited by 28 publications

References 17 publications

Pathway and regulation of erythritol formation in Leuconostoc oenos

Pathway and regulation of erythritol formation in Leuconostoc oenos

Physiological factors affecting total cell number and lipid content of the yeast, Lipomyces starkeyi.

Physiology of yeasts in relation to biomass yields

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