ISSN:
1432-072X
Keywords:
Pyrococcus furiosus
;
Hyperthermophiles
;
Sugar fermentation
;
Non-phosphorylated Entner
;
Doudoroff pathway
;
2-Keto-3-deoxy-gluconate aldolase
;
Glyceraldehyde dehydrogenase
;
2-Phosphoglycerate-forming glycerate kinase
;
ADP-depenent acetyl-CoA synthetase
;
Substrate level phosphorylation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The hyperthermophilic anaerobe Pyrococcus furiosus was grown on maltose as energy and carbon source. During growth 1 mol maltose was fermented to 3–4 mol acetate, 6–7 mol H2 and 3–4 mol CO2. The presence of the following enzyme activities in cell extracts of maltose-grown P. furiosus indicate that the sugar is degraded to pyruvate and H2 by a modified “non-phosphorylated” Entner-Doudoroff-pathway (the values given in brackets are specific enzyme activities at 100 °C): Glucose: methyl viologen oxidoreductase (0.03 U/mg); 2-keto-3-deoxy-gluconate aldolase (0.03 U/mg); glyceraldehyde: benzyl viologen oxidoreductase (2.6 U/mg), glycerate kinase (2-phosphoglycerate forming) (0.48 U/mg), enolase (10.4 U/mg), pyruvate kinase (1.4 U/mg). Hexokinase, glucose-6-phosphate dehydrogenase, 2-keto-3-deoxy-6-phosphogluconate aldolase and phosphofructokinase could not be detected. Further conversion of pyruvate to acetate, CO2 and H2 involves pyruvate: ferredoxin oxidoreductase (0.4 U/mg; T=60°C with Clostridium pasteurianum ferredoxin as electron acceptor), hydrogen: methyl viologen ixodoreductase (3.4 U/mg) and ADP-dependent acetyl-CoA synthetase (1.9 U/mg). Phosphate acetyl transferase and acetate kinase could not be detected. The ADP-dependent acetyl-CoA synthetase catalyzes ATP synthesis via the mechanism of substrate level phosphorylation and apparently constitutes the only ATP conserving site during maltose catabolism in P. furiosus. This novel pathway of maltose fermentation to acetate, CO2 and H2 in the anaerobic archaeon P. furiosus may represent a phylogenetically ancient pathway of sugar fermentation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00290815
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