THE FERREDOXIN-DEPENDENT CONVERSION OF GLYCERALDEHYDE-3-PHOSPHATE IN THE HYPERTHERMOPHILIC ARCHAEON PYROCOCCUS-FURIOSUS REPRESENTS A NOVEL SITE OF GLYCOLYTIC REGULATION

The fermentative conversion of glucose in anaerobic hyperthermophilic Archaea is a variant of the classical Embden-Meyerhof pathway found in Bacteria and Eukarya, A major difference of the archaeal glycolytic p athway concerns the conversion of glyceraldehyde-3-phosphate, In the h yperthermophilic archaeon Pyrococcus furiosus, this reaction is cataly zed by an unique enzyme, glyceraldehyde-3-phosphate ferredoxin oxidore ductase (GAPOR), Here, we report the isolation, characterization, and transcriptional analysis of the GAPOR-encoding gene. GAPOR is related to a family of ferredoxin-dependent tungsten enzymes in (hyper)thermop hilic Archaea and, in addition, to a hypothetical protein in Escherich ia coli. Electron paramagnetic resonance analysis of the purified P. f uriosus GAPOR protein confirms the anticipated involvement of tungsten in catalysis. During glycolysis in P. furiosus, GAPOR gene expression is induced, whereas the activity of glyceraldehyde-3-phosphate dehydr ogenase is repressed, It is discussed that this unprecedented unidirec tional reaction couple in the pyrococcal glycolysis and gluconeogenesi s gives rise to a novel site of glycolytic regulation that might be wi despread among Archaea.