Glucose fermentation to acetate and alanine in resting cell suspensions of Pyrococcus furiosus: Proposal of a novel glycolytic pathway based on 13C labelling data and enzyme activities |
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Authors: | Thomas Schäfer Karina B Xavier Helena Santos Peter Schönheit |
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Institution: | Institut für Pflanzenphysiologie und Mikrobiologie, Freie Universität Berlin, Königin-Luise-Strasse 12-16a;D-14195 Berlin, FRG; Instituto de Tecnologia Química e Biológical, Apartado 127, 2780 Oeiras, Portugal |
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Abstract: | Abstract Suspensions of maltose-grown cells of the hyperthermophilic archaeon Pyrococcus furiosus , when incubated at 90°C with 35 mM 1-13C]glucose or 3-13C]glucose, consumed glucose at a rate of about 10 nmol min−1 (mg protein)−1. Acetate (10 mM), alanine (3 mM), CO2 and H2 were the fermentation products. The 13C-labelling pattern in alamine and acetate were analyzed. With 1-13C]glucose the methyl group of both alanine and acetate was labelled; with 3-13C]glucose only the carboxyl group of alanine was labelled whereas acetate was unlabelled. Extracts of maltose-grown cells contained glucose isomerase (12.8 U mg−1, 100°C), ketohexokinase (0.23 U mg−1, 100°C), and fructose 1-phosphate aldolase (0.06 U mg−1, 100°C). Enzymes catalyzing the formation of fructose 1,6-bisphosphate from fructose 1-phosphate or fructose 6-phosphate could not be detected. As publihed previously by our group and other authors P. furiosus also contains enzymes of glyceraldehyde conversion to 2-phosphoglycerate according to a non-phosphorylated Entner-Doudoroff pathway, of dihydroxyacetone phosphate conversion to 2-phosphoglycerate according to the Embden-Meyerhof pathway, and of 2-phosphoglycerate conversion - via pyruvate - to acetate and alanine. Based on the enzyme activities in P. furiosus , the following pathway for glucose degradation to alanine and acetate in cell suspensions is proposed which can explain the 13C]glucose labelling data: glucose→ fructose → fructose 1- phosphate → dihydroxyacetone phosphate + glyceraldehyde and further conversion of both trioses to alanine and acetate via pyruvate. |
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Keywords: | Pyrococcus furiosus Hyperthermophilic archaeon Novel glucose fermentation pathway Ketohexokinase Fructose 1-phosphate aldolase Embden-Meyerhof pathway Non-phosphorylated Entner-Doudoroff pathway |
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